EPA/AA/CTAB/FE/83-1
Technical Report
The Effect of Initial and Final Production
Volume and MPG Values on Average Fuel Economy
by
Suzanne L. Loos
March, 1983
NOTICE
Technical Reports do not necessarily represent final EPA
decisions or positions. They are intended to present
technical analysis of issues using data which are currently
available. The purpose in the release of such reports is
to facilitate the exchange of technical information and to
inform the public of technical developments which may form
the basis for a final EPA decision, position or regulatory
action.
U. S. Environmental Protection Agency
Office of Air, Noise and Radiation
Office of Mobile Sources
Emission Control Technology Division
Control Technology Assessment and Characterization Branch
2565 Plymouth Road
Ann Arbor, Michigan 48105
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Abstract
The use of manufacturer estimated production can affect the MPG
values used to predict fuel consumption, determine CAFE
compliance, and generate fuel economy general labels.(1)* By
comparing two fuel economy data bases, one containing pre-model
year fuel economies and estimated production (General Label
Files or "D-files") and one containing final model year fuel
economies and actual production (CAFE files or "F-files"), it
is possible to identify fuel economy differences and their
causes, such as sales shifts.
Comparisons of production and MPG differences will be presented
at the fleet level, by manufacturer, and for certain
"battleground" car classes, for each model year from 1978
through 1981.** In addition, the "MPG change allocation"
program (2) identifies causes of the within-year MPG shifts -
weight mix, engine mix, transmission mix, or powertrain
optimization.
* Numbers in parentheses indicate references listed at the
end of this report.
** A preview of the 1982 model year is also included in
Appendix A. While final CAFE data on a car-by-car basis
are not yet available for 1982, mid-year estimates
submitted to DOT have been acquired and analyzed.
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Purpose
This study was done at this time for three reasons:
1) Data of "final CAFE" vintage now exists for four model
years -- the data are quite complete for 1978 through 1980,
and reasonably complete (most major manufacturers) for
1981. This state of affairs now permits a first look for
trends in projected-to-actual production and MPG
relationships;
2) Stories are beginning to appear in the media* regarding a
growing number of manufacturers whose recent MPG forecasts
for model year 1983 are falling short of the MPG standards,
and far short of their earlier projections. While of
course we cannot yet compare 1983 projections with 1983
actuals, it is pertinent to examine the earlier years' data;
3) The standard procedure for fuel economy trend analysis has
been to accept the manufacturers' pre-model year general
label data, and to stick with that until final CAFE figures
appear two or three years later. If there is any sign of a
growing divergence between projections and actuals, it may
be necessary to take new approaches, such as (a) closer
scrutiny of, and possibly even the application of "judgment
factors" to, the projections, and/or (b) acquisition of
intermediate updated estimates available before the
sometimes-long-delayed CAFE figures are finalized.
Wall Street Journal, February 7, 1983, pg. 10;
Automotive News, Feburary 21, 1983, pg. 26.
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Background
In order to understand how sales shifts can affect fuel economy
projections it is neccessary to provide some background on
certain aspects of the EPA Fuel Economy Program.
The following sections will concentrate on three areas:
- Uses of Production Volumes
- Production Volume Weighting of Fuel Economy
- How MPG Changes During the Course of a Model Year
Uses of Sales/Production Volumes
Before each model year, manufacturers are required to submit
estimates of production volumes for fuel economy labeling
purposes. Estimated production volumes are used to calculate
sales weighted fuel economy general labels and were used to
calculate preliminary CAFE*(Corporate Average Fuel Economy).
Estimated production volumes are also used to determine the
emission and durability fleets submitted to EPA as a portion of
the Application for Certification. After each model year,
manufacturers are required to submit their actual production
volumes to determine CAFE compliance as required under the
Energy Policy and Conservation Act (EPCA).
During the production of vehicles of a given model year,
manufacturers label each new vehicle with a model type fuel
economy called the general label. The general label is a
production volume weighted fuel economy number. These fuel
economy values come from two sources: the original emission
Preliminary CAFE calculations are no longer required.
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certification test fleet and additional fuel economy data
vehicles usually projected to be a manufacturer's high seller
within a base level. Details of the fuel economy production
volume weighting scheme will be presented in the next section.
The preliminary CAFE was used to provide a basis for
determining additional testing requirements due to product line
changes or additions to a product line. (1) This was done to
make the fuel economy data base more representative of a
manufacturer's final product line. General label fuel economy
data with updated production volumes were also included in the
PCAFE data base.
The final CAFE calculated in compliance with EPCA includes all
fuel economy data from the sources previously mentioned plus
any additional running changes.* The important difference from
the earlier estimates is that the CAFE production volume
weightings are based on a manufacturer's actual production.
Production Volume Weighting of Fuel Economy
A general label MPG value is defined as a production volume
weighted average of base level fuel economies for a particular
model type. For a general overview and definition of basic
terms of the production volume weighting hierarchy see Table
1. At a glance it may look like numerous tests are required to
calculate -a single Model-Type fuel economy label. However,
this is usually not the case. A minimum of one test
(subconfiguration) per base level is all that is needed to meet
fuel economy testing requirements, and it is not necessarily
the highest seller.
*(Running changes for base level(s) which represent 1% or
more of a manufacturers' fleet).
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Table 1
Levels of Fuel Economy Sales Weightings (3)
Sales Weighting
Level
Model Type
Base Level
Configuration
Subconf iguration
Definition
A unique combination
of car line, basic
engine and trans-
mission class.
A unique combination
of basic engines,
inertia weight and
transmission.
A unique combination
of basic engine,
engine code, inertia
weight, transmission
class and axle ratio
within a base level.
A unique combination
of basic engine,
engine code inertia
weight, transmission
class axle ratio,
estimated test weight
and road load horse-
power.
EE Uses
General Label
EPA/DOE GUIDE
D-FILES*
F-FILES
Specific
Labels
Specific
Labels
Comments
Usually two "base
levels" sales
aggregate into a
"Modal Type".
Several "configu-
rations" are sales
aggregated within
each "base level".
Several "subcon-
figurations" are
sales aggregated
within a "con-
figuration" .
Represents one
test vehicle.
* FE Trend Analyses.
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In other words, the fuel economy values for one vehicle may
represent the fuel economies of several vehicles contained
within its configuration and/or base level when production
volume weighting is used.
How MPG Changes During the Course of a Model Year
When a manufacturer requests a fuel economy general label it is
prior to actual production of the vehicle so a prototype
vehicle is used to test for fuel economy. A general label is
calculated using this type of data.
Often after a general label is issued, a manufacturer may want
to implement a design change (or "running change") to vehicles
in their product line. This may result in a fuel economy
difference that is not reflected in the general label since no
recalculations are required. If the sales attached to that
running change are significant it could result in a different
MPG value than reflected on that label.
Running changes include, for example, changes in the engine
calibration, which could create untested engine codes, and
addition or removal of weight.
Projected vs Actual Production Volume Analysis for Model Year
1978-1981
This section will present 55/45 MPG, average inertia weight and
average displacement, production volume weighted using both
projected and actual figures by various strata for model years
1978-1981. The percent difference (%DIFF) is also given for
each within-year comparison. In addition a ratio of projected
to actual production volumes is presented as a measure of over-
or under-projection of production for each model year.
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The Fleet
Table 2 presents percent differences of 55/45 fuel economy,
average inertia weight and displacement at the fleet level for
model years 1978-1981. It is important to note that the 1981
final CAFE data base used in this study is not the complete
fleet (some manufacturers are missing); comparisons were made
against a comparable 1981 D-file (with the same manufacturers
omitted). Aggregation at the fleet level includes all
manufacturers labeled and certified for U.S. sale during any
given model year unless otherwise specified.
For most model years presented, sales seemed to shift slightly
to favor lighter, more fuel efficient fleets than that
projected at the start of the model year.
Individual Manufacturer Fleets
Percent differences of 55/45 MPG, average inertia weight and
average displacement are also presented by manufacturer in
Table 2 for model years 1978-1981. The domestic manufacturers
had a tendency to overproject production but in most cases
ended up with lighter more fuel efficient fleets based on
actual production. Most foreign manufacturers underprojected
production for the years listed. For some manufacturers (Fiat
and JRT) there were very large differences between projected
and actual production. Most manufacturer's %DIFF values show
that when weight and displacement go down, fuel economy goes up
and vice versa.
The large changes in fuel economy (1978 Peugeot for example)
are attributed in most cases to late model introduction or
elimination of a model from a manufacturer's product line
altogether. A detailed analysis later in this report helps to
pinpoint specific sales shift effects (e.g. weight mix,
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General Motors
Ford Motor Co.
Chrysler
Toyota
Ntssan (Oatsun)
vw-Audl -Porsche
Honda
Mazda
Mt tsuotshl
Subaru
American Motors
Volvo
Mercedes-Benz
BLMC (ORT)
BMW
Renaut t
Saab
Peugeot*
I suzu**
Fleet
MODEL YEAR 1978
18. 83
3818
296. 1
1.078
18.33
3952
291.3
0.946
17.80
3362
282.4
1.080
27. 12
2621
111.7
0.723
26.27
2574
114.7
0.884
29.03
24O4
97.5
1.289
33.74
21 13
89.5
O.SI3
35. 13
2270
78.0
0.820
3O.47
2627
112.5
O.660
31.63
2351
97.0
0.639
19. OS
3452
244.8
1 .226
2 1 . 56
2529
96.4
1 . 115
21.11
3347
138.2
0.916
19. 16
3970
203. 1
0.994
2O. 8O
2778
127.2
2.372
19.99
2929
135.5
0.935
29.84
2079
81.3
0.547
22.66
3OOO
122.0
0.912
21 .24
3500
143.5
0.969
26.79
2500
111.0
0.812
19.57
3649
261.9
1 .015
O.9
-0.6
-2. 1
*1 .3
-1.7
-4. 1
1.2
-1.8
-2.8
-1.1
0.0
0.8
1 .9
-1 .6
-3.3
-6.4
-0.2
O.3
-0. 1
0.6
0.9
1.1
-0.0
0.0
O.4
0.3
2.2
-5.4
1.1
0.0
-2.6
2.3
2.5
*O . 8
O.3
2.6
0.5
-0.0
-0.2
-2.5
0.0
2.7
1.7
-0.2
-4 .5
-1.7
2.0
2.5
1 .7
-1 .6
-1.2
0.4
0.0
0.0
16.9
0.0
-3.8
0.3
0.0
0.0
1.6
-1 .6
-3.9
19.00
3794
289.9
18 56
3885
279.4
18.01
3892
274.5
26.82
2622
112.6
26.77
2534
1 10.9
27. 17
241O
97.8
33.72
2126
90.3
35.52
2269
78. 0
30.59
2636
115.0
29.93
2376
97.0
18. SB
3532
250.9
2537
98.9
21.21
3346
137.9
18.68
3971
208.5
21 . 16
2772
121.5
19.65
2988
138.9
30.34
2045
80.3
22.76
3000
122. 0
24.83
3500
138.0
26.86
2SOO
111.0
19.89
3589
251.6
MODEL YEAR 1979
Protected ItDIFF Actual
19. 18
3777
286.2
0.984
18.40
3675
254.4
1.072
19.82
3670
2S3.3
1. 174
24. 13
2713
112.8
0.988
26.43
2555
1 12.8
1.068
30.65
2388
97.0
1.426
31.22
2245
95.2
1 ,01O
27.48
2458
80.7
0.567
3O. 15
2524
113.2
1 .363
29.25
2394
97.0
0.786
19.60
3379
239.4
1 .092
24 . 64
2514
106. 1
0.581
20.68
3347
138.8
1.008
20. 14
3967
199.5
0.967
20. 80
2830
131.9
1.536
20.25
3062
140.7
0.989
30.06
2056
80.6
1.777
22.66
3000
122.0
1 .061
26.30
3500
136.9
0.820
29.01
2500
111.0
1.993
20. 11
3507
24Q.8
1.034
-0.3
-0.3
-0.6
4.2
-1.5
-2.4
1.4
-2.6
-5 .8
-0.5
-0.4
0.0
1.6
-2.4
-3.5
-6.8
O.2
0.9
-7.0
2.8
2. 1
-6.7
3.9
3.2
7. 1
-6.5
-8.7
1 .0
O.4
0.0
1.6
0.0
-2.9
+7 . 0
-0.0
-1.7
1 .7
-1.2
-3.3
1.7
-0.4
2.0
2. 1
-4.2
-8. 1
-0.9
0.3
0.0
-0.8
0.2
0.2
-4.2
0.0
-O.8
-9.4
0.0
5. t
0.3
0.0
0.0
O.7
-0.6
-1.1
19. 13
3764
284.6
19. 18
3621
248.2
20. 09
3576
238.7
24.00
2701
112.8
26.84
2494
IO8.9
28.56
2389
97.9
29.03
2308
97.2
25.63
2554
83.3
32.29
2359
103.4
29.54
24O4
97.0
19.91
3379
232.4
26 . 36
2513
104.3
21.04
3308
134.2
20.48
395O
203.4
21 .24
2712
121.2
20.07
3071
140. 7
3O.3I
2O61
80.8
21.70
30OO
121 .0
23.83
3500
143.9
29. 10
2500
111.0
20.26
3485
238. 1
55/45 MPQ. inertia
MODEL YEAR 1980
Prelected %OIFF Actual
21 .30
3500
240.6
1 .209
21.71
3406
229.9
1 .706
19.99
3498
231 .6
1.736
26.57
2608
1 19.6
0.788
30.45
25O7
1 10.4
0.845
30.53
2403
100.9
0.803
30.47
2254
96.6
1.01O
26.89
2455
84.7
0.704
30.70
2451
114.3
0.979
27.81
2382
99. 0
0.779
22.00
316O
208. 1
1. 100
27 . 80
2609
IO5.0
2.205
20.79
3276
139.3
0.961
24.61
3705
190. 1
1.673
21 .58
2817
133. 0
1.692
25.28
3O61
132.0
1 .066
33.23
2000
85.0
0.991
23.23
2963
121 .0
1 .246
27.62
3500
137.3
-
NA
22.37
3283
210.9
1.239
2.8
-3.3
-6.4
3.4
-6.4
-10.3
8.5
-8.8
-17.1
3. 1
0.5
-3.9
2.6
-1 .8
-5. 2
2.6
-0.4
-1 .6
-4.2
3.4
3. 1
-3.2
4.2
8.3
6.0
-4 . 1
-7.5
1.2
O.8
-O. 1
-2.2
2.4
7.4
0.8
4.2
3.G
0.5
-0.8
-2.8
2. 1
2.8
-O. 1
-1.1
-2.7
2.4
-1 .8
-3.3
0.2
0.0
0.0
O.6
-O. 1
O.O
NA
NA
5. 1
-5.6
-11.1
21 .89
3384
225. 1
22.45
3187
206.3
21 .69
3189
192.0
27.40
2620
114.9
31 .23
2461
1O4 . 7
31.32
2394
99.3
29. 18
2330
99.6
26.02
2559
91.8
32.53
2351
105.7
28. 13
2402
98.9
21 .51
3237
223.6
26 . 59
2629
109.4
21.54
3294
138.2
23.92
3781
195.5
21.55
2787
129.4
25.88
3005
127.7
33.29
2OOO
85.0
23.36
2961
121 .0
NA
NA
23.51
31OO
187.4
Weight. Displacement
MODEL YEAR
Protected 7.0 IFF
23.36
3456
225.5
1 .025
23.23
3151
187.4
1 .085
25.63
2912
167. 1
1.408
3O.30
2653
121 .5
0.823
31.46
2482
109.2
0.938
NA
30.95
23O3
97.9
1.009
31 . 12
2362
92.7
1.078
31.68
2358
105.0
0.969
30.37
2382
1O6.8
0.748
NA
27 . 46
2633
1 10.4
2.577
23.53
3390
136.5
0.905
25. IS
3745
184.0
0.986
17.42
40OO
258.0
0.881
26.79
2924
121 .4
1 .056
NA
23.67
2971
121.0
1 .852
28.36
350O
138.8
1.082
29.97
2500
111.0
O.525
24.91
3126
185.3
1.048
-0.9
-0.2
0.8
O.5
-2.7
-1.0
1.6
-2.4
-5.9
1.9
-3.6
-6.3
-3. 1
1 .9
3.2
NA
-0.5
1 .7
1.8
-0.2
3.7
5.4
0.9
-0.6
1.4
3.0
O.8
0.2
NA
O. 5
-1.6
1.7
-5.4
-0.2
-2.5
1.7
0. 1
0. 1
6.4
-6.O
-8.8
-0.9
0,8
1.4
NA
-1.8
O.4
0.0
-1.4
0.0
-0.3
15.7
2.2
0.0
0.1
-O.9
-O.7
1981'"
Actual
23. 15
3449
227.2
23.34
3066
185.5
26.05
2841
157.3
30.89
2557
113.9
30.50
2530
112.7
NA
3O.80
2343
99.7
31.07
2449
97.7
31.97
2345
1O6. 5
31 .27
24OO
1O7.0
NA
27 . 60
2591
112.3
22.27
3382
133. 1
25.59
3747
184.2
18.54
3760
235.3
26.55
2946
123. 1
NA
23.24
2984
121.0
27.95
35OO
138.4
34.68
2556
111.0
24.94
3098
184. 0
' 1980 Peugeot final CAFE was never calculated, used estimated data to calculate a final fleet number for Peugeot.
** Isuzu imported no passenger cars tn Model Year 198O.
* The 1981 Final Fleet is not complete at this time, however a truncated Projected Fleet was used for the 81 comparisons
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transmission mix, etc.) on fuel economy at the manufacturer and
fleet levels.
Leading Car Classes
Percent differences for 55/45 MPG, average displacement and
average inertia weight are presented in Table 3 for the leading
car classes. The Midsize and Large car classes reveal a
tendency to overproject production most years, while Subcompact
and Compact car classes show underprojection of production.
The actual competition battlegrounds for the years of interest
are Subcompact and Midsize with Large and Compact vehicles
competing for third place. Actual fuel economy differences
within each model year are either slightly higher or lower with
no definitive pattern. Note the 1980 production overprojection
by a factor of two for Large cars.
Newly-Introduced Model Types
Percent differences for 55/45 MPG, average displacement and
average inertia weight are presented in Table 4A for selected
model types. These are new models introduced during model year
1978 through 1980; their manufacturers' predictive abilities
are tracked from introduction up until 1981. There does not
seem to be any substantial MPG gains or losses within a model
year due to sales shift even at the specific model type level.
The domestics still continue to overproject production more
than underproject for new models. The imports generally
undejrprejected production (although Fiat generally has tended
to overproject by large amounts as is illustrated by the Brava
data).
-------
Table 3
% Difference by Car Class Leaders 1978-1981
Car Class
Subcompact
55/45 MPG
Inertia Weight
Displacement
Projected Sales/Actual Sales
55/45 MPG
Inertia Weight
Displacement
Projected Sales/Actual Sales
Midsize
55/45 MPG
Inertia Weight
Displacement
Projected Sales/Actual Sales
55/45 MPG
Inertia Weight
Displacement
Projected Sales/Actual Sales
Projected
24.61
2870
163.7
0.939
19.78
3613
242.1
0.945
18.65
3800
293.1
1.109
16.77
4391
358.0
1.074
1978
% Dif f
+0.0
-0.9
-2.6
+2.0
-1.7
-2.7
-0.5
+0.5
-0.4
+0.2
+0.1
-0.3
Actual
24.62
2844
159.5
20.17
3550
235.6
18.56
3820
292.0
16.80
4394
357.1
Projected
24.35
2836
153.5
1.018
19.07
3663
247.2
0.943
18.90
3734
277.7
0.999
17.36
4198
336.3
1.093
1979
% Diff
-0.8
+0.2
+0.9
+1.9
-1.0
-0.8
+1.1
-0.6
-1.9
+0.1
+0.3
+0.9
Actual
24.15
2843
154.9
19.44
3628
245.3
19.11
3710
272.4
17.37
4210
339.4
Projected
26.21
2721
138.4
0.949
22.40
3218
191.1
1.052
21.25
3416
239.8
1.279
18.79
4158
315.7
1.989
1980
% Diff
+3.4
-2.9
-7.7
+1.8
-2.4
-4.9
+1.7
-1.6
-4.7
+1.4
-0.7
-0.6
Actual
27.11
2643
127.8
0.969
22.81
3141
181.7
21.62
3362
228.5
19.06
4130
313.8
1981
Projected
28.69
2664
127.8
27.75
2776
132.1
0.901
23.26
3329
215.4
1.167
20.66
4086
294.6
0.955
% Diff
Actual
+0.5 28.83
-1.4 2626
-2.0 125.2
-0.8 27.52
-0.6 2758
+1.5 134.1
-1.3 22.95
+0.5 3346
+2.0 219.8
-1.2 20.41
+0.5 4108
+3.3 304.4
-------
Table 4A
% Difference by Newly-Introduced Model Types 1978-1981
Model Types
Chtysler Omni/Horizon
55/45 MPG
Inertia Weight
Displacement
Projected Sales/Actual Sales
Ford Fairmont/Zephyr
55/45 MPG
Inertia Height
Displacement
Projected Sales/Actual Sales
General Motors X-Cars
55/45 MPG
Inertia Weight
Displacement
Projected Sales/Actual Sales
Fold Fiesta
55/45 MPG
Inertia Weight
Displacement
Projected Sales/Actual Sales
Fiat Brava
55/45 MPG
Inertia Weight
Displacement
Projected Sales/Actual Sales
Honda Prelude
55/45 MPG
Inertia Weight
Displacement
Projected Sales/Actual Sales
Toyota "tercel
55/45 MPG
Inertia Weight
Displacement
Projected Sales/Actual Sales
Datsun 310
55/45 MPG
Inertia Weight
Displacement
Projected Sales/Actual Sales
H-M 528 I
55/45 MPG
Inertia Weight
Displacement
Projected Sales/Actual Sales
1978
Projected Actual
% Diff
26.28 +4.8 27.54
2500 0.0 2500
105.0 0.0 105.0
0.710
20.73 -1.0 20.52
3212 -0.5 3196
226.4 -4.2 216.9
1.112
N/A N/A N/A
37.39 -0.2 37.32
2000 0.0 2000
98.0 0.0 98.0
1.140
N/A N/A N/A
N/A N/A N/A
N/A N/A N/A
N/A N/A N/A
N/A N/A N/A
Projected
27.52
2523
105.0
1.022
19.94
3150
207.1
1.035
N/A
31.85
2000
98.0
0.941
25.09
2750
122.0
0.814
N/A
N/A
N/A
20.00
3500
170.0
1.108
1979
% Diff
+0.4
-0.0
0.0
+6.2
-1.0
-4.7
N/A
+0.7
0.0
0.0
+1.2
0.0
0.0
N/A
N/A
N/A
+0.2
0.0
0.0
Actual
27.62
2522
105.0
21.17
3130
197.3
N/A
32.07
2000
98.0
25.40
2750
122.0
N/A
N/A
N/A
20.04
3500
170.0
Projected
26.79
2484
105.0
0.994
23.46
3028
181.7
1.076
24.80
2886
163.0
0.947
29.93
2000
98.0
, 0.789
24.83
2964
122.0
2.345
27.10
2500
107.0
0.813
34.36
2184
89.0
0.669
34.58
2250
85.0
0.428
21.24
3500
170.0
1.259
1980
% Diff
+0.9
-0.6
0.0
-1.1
-0.0
+1.8
-1.0
+0.2
-0.1
-0.4
0.0
0.0
-2.3
-1.0
0.0
+0.3
0.0
0.0
+0.9
+0.6
0.0
-1.0
0.0
0.0
+0.4
0.0
0.0
Actual
27.04
2469
105.0
23.20
3027
184.9
24.54
2892
162.9
29.81
2000
98.0
24.26
2933
122.0
27.18
2500
107.0
34.68
2198
89.0
34.22
2250
85.0
21.33
3500
170.0
1981
Projected
31.10
2448
105.0
1.611
22.83
3114
184.3
1.158
25.71
2946
156.8
1.062
N/A
26.67
2971
122.0
3.659
28.36
2500
107.0
0.905
36.70
2250
89.0
0.622
34.48
2250
91.0
0.951
21.31
3500
170.0
0.914
% Diff
Actual
+4.6 32.52
-1.0 2424
0.0 105.0
-3.6 22.01
+0.0 3115
+2.0 188.0
-0.6 25.55
+0.3 2954
+1.5 159.2
N/A N/A
+2.3
-1.3
0.0
+1.4
0.0
0.0
-0.1
0.0
0.0
+0.5
0.0
0.0
0.0
0.0
0.0
27.27
2933
122.0
28.76
2500
107.0
36.65
2250
89.0
34.64
2250
91.0
21.31
3500
170.0
-------
-13-
Table 4B rearranges the projected-to-actual production volume
ratios for the new models to shed some light on the accuracy of
projections as a function of time since introduction.
Excluding Fiat, an obvious outlier, the average error
(unsigned) in predicting production improves significantly in
the second year and only marginally in the third year.
Table 4B
Projected/Actual Production Ratio, New Models
Chrysler Omni/Horizon
Ford Fairmont/Zephyr
GM X-Cars
Ford Fiesta
Fiat Brava
Honda Prelude
Toyota Tercel
Datsun 310
BMW 5281
1st Year
0.71
1.11
0.95
1.14
0.81
0.81
0.67
0.43
1.11
2nd Year
1.02
1.04
1.06
0.94
2.35
0.91
0.62
0.95
1.26
3rd Year
0.99
1.08
-
0.79
3.66
-
-
-
0.91
RMS Error 0.22 0.12 0.10
(excluding Fiat)
Analyses using the "Allocation Method"
The allocation program which has been used in the past to
identify specific causes of year-to-year fuel economy changes
was used here to determine specific causes of within year fuel
economy changes. Specific background on the allocation method
is available in Appendix B (an excerpt from SAE Paper No.
790225).
-------
-14-
The specific areas the allocation method analyzes are listed in
Table 5.
Class Name
1. Powertrain
Optimization
2. Transmission
Mix Shifts
3. Engine Mix
Shifts
4. Weight Mix
Shifts
Table 5
Total Fuel Economy Change(2)
Divided In To Four Classes
Isolates Changes
Due to
a) Engine Design changes
b) Emission Control System
Changes
c) Transmission Design
Changes
d) Change in Test Procedure
Changing proportion of
transmission types.
a) Changing proportion of
different engine dis-
placements
b) Change in Gasoline/
Diesel mix
a) Changes in sales of
different IW classes
b) Introduction/Termi-
nation of Models
Example
1. Change from no-
catalyst to oxi-
dation catalyst,
recalibration, (a)
and (b).
2. Change from A3
transmission to L4
transmission (c).
3. Road load
change in 1979,
(d).
Change to more
manual trans-
missions.
1. More smaller
displacement
engines, (a).
2. More Diesels,
(b) .
1. More light-
weight cars (a) .
2. Addition of a
new model with a
new weight class.
The results for the allocation method will be presented by
individual manufacturer and the fleet level in Tables 6 through
9 for model years 1978-1981. Additional results for specific
car classes (Subcompact and Midsize) will be presented in
Tables 10 through 17 respectively for model years 1978-1981.
-------
Table 6
Allocation of Fuel Economy Changes from 1978D to 1978F
for Passenger Car Fleet
Percent Fuel Economy Change due to :
Manufacturer
American Motors
Chrysler Corp.
Ford Motor Co.
General Motors
BMW
Mercedes-Benz
Fiat-Lanc-Frari
Honda
Isuzu
Jag-Rov-Tr 1
Nissan (Datsun)
Peugeot
Renaul t
Saab
Mitsubishi
Mazda
Toyota
VW-Audi -Porsche
Vol vo
Subaru
1978D*
Car
SwMPG
19. 1
17.8
18.3
18.8
2O. 0
19.2
21 .6
33.7
26.8
2O. 8
26.3
21.2
29.8
22.7
3O.5
35. 1
27. 1
29. O
21.1
31.6
Powertra In
Opt im1-
zat Ion
0.3
-0.5
-0.7
O.O
O.O
O.O
1 .3
-0.4
0.5
0.7
-O.6
-0.4
-0. 1
-0.3
0.2
-0.4
-O.5
-O.6
-0.5
-3.8
Transmls-
s Ion M 1 x
Shifts
-0
0
-O
O
O.
O.
O.
O.
-0,
O.
-O.
O.
O.
-0.
0.
1 .
- 1 .
O.
O.
-1 .
.3
.3
.2
.O
2
.O
.4
.0
, 1
O
3
6
0
2
1
1
O
1
2
0
Engine
Mix
Shifts
O.3
-0.2
0.7
O.3
O.O
-2.5
-0.2
0.3
-0. 1
-2 .3
O.3
16.6
0.6
0.9
0.8
0.3
O. 1
-5.6
O.7
1 .3
Weight
Mix
Shifts
-2.9
1 .5
1 .4
O.6
-1.8
-0. 1
-O.5
O. 1
O.O
3.4
2 .6
O.O
1 .2
0.0
-O.7
O. 1
O.2
-O.4
O.O
-1.9
Al 1
Changes
Combl ned
-2
1
1
O
- 1
-2 .
O.
-O
O.
1
1 .
16
1
O
0.
1 .
- 1 .
-6.
O.
-5.
.7
. 1
.3
.9
. 7
.6
.8
. 1
.3
.7
9
9
.7
4
4
1
1
4
5
4
1978F*
Car
SwMPG
18
18
18
19
19.
18.
21
33
26.
21 .
26.
24,
3O.
22.
3O.
35.
26.
27.
21 .
29.
.6
.0
.6
.O
.7
.7
. 7
.7
.9
2
8
.8
3
8
6
5
8
2
2
9
1
Ln
1
FLEET
19.6
-0.3
* D means projected; F means actual
0.0
0.2
1 .7
1 .6
19.9
-------
Table 7
Allocation of Fuel Economy Changes from 1979D to 1979F
for Passenger Car Fleet
Percent Fuel Economy Change due to
Manufacturer
American Motors
Chrysler Corp.
Ford Motor Co.
General Motors
BMW
Mercedes-Benz
F iat-Lanc-Frar i
Honda
Isuzu
Jag-Rov-Tr i
Nissan (Datsun)
Peugeot
Renaul t
Saab
Mi tsubishi
Mazda
Toyota
VW-Audi -Porsche
Volvo
Subaru
1979D
Car
SwMPG
19.6
19.8
18 .4
19.2
20.3
20. 1
24.6
31 .2
29. O
2O. 8
26.4
26.3
3O. 1
22 .7
3O. 1
27.5
24. 1
30.6
20.7
29.3
Powertraln
Opt imi-
zat ion
O.2
-1 .0
3.O
-O.7
O.O
0.7
1 .3
-4.6
-0. 1
-1.3
-0.5
-2. 1
O.4
-4.5
-O. 1
-O.5
-1.3
O.O
-0.5
0.0
Transmis-
sion Mix
Shifts
-O. 1
O.2
O. 1
O. 1
0.0
-0.6
-0.5
1 .4
-O.4
O.O
0.0
0.4
0.0
O.6
-O.9
-0. 1
0.0
1 .2
0.0
1 .0
Engine
Mix
Shifts
1
-0.
-0
0
-0
0
5
-2
O.
-1 .
-o.
-7.
0.
-O.
-o.
2.
O.
-7 .
1 .
0.
.4
.2
. 1
. 1
. 1
.3
9
.4
9
.7
.6
9
7
4
1
6
2
3
8
5
Weight
Mix
Shifts
O
2
1
O
-0
1
0
- 1
0.
5.
2.
0.
-o.
0.
8 .
-8.
0.
-0.
0.
-o.
.2
.4
.2
. 3
.7
.2
,2
.6
O
2
.6
0
2
0
4
6
6
6
4
6
Al 1
Changes
Comb ined
1
1
4
-O
-o
1
7
-7
o
2
1
-9
0
-4
7
-6
-O.
-6.
1 .
1 .
.6
.4
. 2
.3
.9
.6
.O
.O
. 3
. 1
.6
.4
.8
.2
. 1
. 7
.5
8
7
0
1979F
Car
SwMPG
19
2O
19
19
2O
20
26
29
29
21
26
23
3O
21
32
25
24
28
21 .
29.
.9
. 1
.2
. 1
. 1
.5
.4
1
.O M
CTi
1 '
. 2
.8
.8
.3
.7
. 3
.6
.O
6
0
5
FLEET
2O. 1
0.2
0.0
-O. 1
O.6
O.7
2O. 3
-------
Table 8
Allocation of Fuel Economy Changes from 198OD to 1980F
for Passenger Car Fleet
Percent Fuel Economy Change due to
Manufacturer
American Motors
Chrysler Corp.
Ford Motor Co.
General Motors
BMW
Mercedes-Benz
F ia t-Lanc-Frar i
Honda
Jag-Rov-Tr i
Nissan (Datsun)
Renaul t
Saab
Mi tsubi shi
Mazda
Toyota
VW-Audl -Porsche
Volvo
Subaru
19 800
Car
SwMPG
22
20
21
21
25
24
27
30
21
30.
33
23.
30.
26.
26.
30.
2O.
27.
.O
.O
.7
.3
.3
.6
.8
.5
.6
.4
.2
.2
. 7
.9
6
5
8
8
Powertrain
Optimi-
zat ion
-O. 1
-O.8
-1.3
-1.1
0.0
0.4
-2.3
-1.2
-0.5
-1 .6
-O.2
-O. 1
O.2
.0.0
1 .3
-0.6
O.O
2.3
Transmi s-
sion Mix
Shifts
0. 1
0.0
0. 1
0.0
0. 1
O. 1
0.9
O.3
0.0
-0.3
O.O
O.6
0.2
0.2
1 .4
0.2
0.0
O.O
Engine
Mix
Shifts
-0.5
0.4
0. 1
1 .4
0.0
-1.2
-1 .O
O.O
-O.4
O.6
O.4
0.0
0.2
4.O
2.0
1 .9
3.6
O.3
Weight
Mix
Shifts
-1
9
4
2
2
-2
-2
-3
0
3
O
0
5
-7
-1
1
-o,
- 1 .
.7
.O
.6
.4
.3
.2
.0
.4
.7
.9
.0
.O
.3
.2
.6
. 1
O
5
Al 1
Changes
Combined
-2
8
3
2
2
-2
-4
-4
-o
2
0
O
5
-3
3 .
2
3.
1 .
.3
.5
.5
.8
.4
.8
.4
. 2
.2
.6
.2
.6
.9
.2
. 1
.6
6
2
198OF
Car
SwMPG
2 1
21
22
21
25
23
26
29
21
31
33
23 .
32 .
26.
27 ,
31 .
21 .
28.
.5
.7
.5
.9
.9
.9
.6 1
r
.6
.2
.3
.4
.5
,O
.4
.3
.5
1
FLEET
22.4
-1 .O
0. 1
0.9
5.0
5. 1
23.5
-------
Table 9
Allocation of Fuel Economy Changes from 19810 to 1981F
for Passenger Car Fleet
Percent Fuel Economy Change due to
Manufacturer
Chrysler Corp.
Ford Motor Co.
General Motors
BMW
Mercedes-Benz
F iat-Lanc-Frar i
Honda
Isuzu
dag-Rov-Tr i
Nissan (Datsun)
Peugeot
Saab
Mi tsubishi
Mazda
Toyota
Volvo
Subaru
1981D
Car
SwMPG
25.6
23.2
23.4
26.8
25. 1
27.5
3O.9
3O.O
17.4
31 .5
28.4
23.7
31.7
31.1
3O.3
23.5
30.4
Powertra in
Opt imi -
zat ion
-O
- 1
-O
0
1
1
-0
-O
-0
- 1 .
-0.
- 1
0.
-O.
-1 .
-0.
3.
.9
.9
.7
.O
.9
.3
1
.6
.7
2
,7
6
O
4
O
4
6
Transmis-
s ion Mix
Shifts
-0. 1
0.2
0.0
O.O
-o.o
0.4
1 .2
O.2
0.0
-0.6
-O.2
O.6
O.5
1 . 3
-O.4
0.0
0.5
Engine
Mix
Shifts
-O
-1
-O
0
-0
-2
O
15
0.
0.
-0.
O.
-0.
1 .
O.
-5.
0.
.0
.3
.4
.O
. 1
.3
.2
.9
.5
5
.5
,O
9
O
2
1
1
Weiqht
Mix"
Shifts
2 . 7
3.5
0.2
-O.9
-o.o
1 . 1
-1.7
O.2
6.7
-1.6
0.0
-O.9
1 .3
-2 .0
3. 2
O. 1
-1.2
Al 1
Changes
Comb ined
1
O
-0
-0
1
0
-0
15
6
-3.
- 1 .
- 1 .
O.
-O.
1 .
-5.
3.
.6
.5
.9
.9
.7
.5
.5
.7
.4
1
4
8
9
2
9
4
0
1981F
Car
SwMPG
26
23
23
26
25
27
30
34
18
30.
27.
23
32 .
31 .
3O.
22 .
31 .
. 1
.3
. 1
.6
.6
.6
.8
.7
.5
.5
.9
.2
,O
1
9
3
3
1
oo
1
FLEET
24 .9
-0.8
O. 1
-O.5
1 . 4
O. 1
24 .9
-------
Table 1O
Allocation of Fuel Economy Changes from 1978D to 1978F
for Subcompact Passenger Cars
Percent Fuel Economy Change due to
Manufacturer
American Motors
Ford Motor Co.
General Motors
BMW
Mercedes-Benz
Fiat-Lanc-Frari
Honda
I suzu
Jag-Rov-Tr i
Nissan (Datsun)
Mazda
Toyota
VW-Aud1 -Porsche
1978D
Car
SwMPG
21.4
37.4
20.8
20.0
0.0
20.0
34.7
26.8
13 . 1
24.5
35.5
27.3
31.9
Powertrain
Opt Imi -
zat ion
-0. 1
-0.5
-0.5
0.0
O.O
1 . 1
-0.8
O.5
8.8
-0.8
-O.5
-O.4
-0.4
Transmi s-
sion Mix
Shifts
-O
0
-0
0
0,
O.
0.
-0.
O.
-O.
1
- 1 .
-O.
.2
.0
.0
.2
,O
9
.O
. 1
0
.1
2
O
2
Engine
Mix
Shifts
1
O
-O
O
O
O,
O.
-O
-2.
O.
O.
O.
-7.
.9
.3
.3
.0
,0
,0
.2
. 1
.8
.0
.3
1
1
Weight
Mix
Shifts
-3
O
2
-o.
O.
7 c
O
0
0
8 .
O.
0.
O.
.O
.0
.0
.4
,O
.6
.O
0
O
.5
4
2
3
Al 1
Changes
Combined
- 1
-O
1
-0
O
9
-O.
O
5
7 .
1 .
- 1 .
-7 .
.5
.2
.2
.3
.O
.8
.5
.3
.7
6
.4
2
3
1978F
Car
SwMPG
21.1
37 .3
21 .0
19.9
14.2
22. O
34 .5
26.9
13.8
26.4
36. O
27. O
29.6
FLEET
24.6
-O.4
-0.2
-1 .0
1 .6
O.O
24 .6
-------
Table 11
Allocation of Fuel Economy Changes from 19790 to 1979F
for Subcompact Passenger Cars
Percent Fuel Economy Change due to
Manufacturer
American Motors
Chrysler Corp.
Ford Motor Co.
General Motors
BMW
Mercedes-Benz
Fiat-Lanc-Frari
Honda
Isuzu
Jag-Rov-Tr i
Nissan (Datsun)
Mitsubishi
Mazda
Toyota
VW-Audl -Porsche
1979D
Car
SwMPG
2O. 8
27 .5
22.8
21.3
21.3
0.0
24.7
30. 1
29 .0
11 .0
28.2
31.2
33.6
24.2
33.6
Powertra in
Opt imi -
zat ion
O.
-1
2
-0.
0.
0,
-O.
- 1 .
-O.
O.
-1 .
-0.
-O.
- 1 .
O.
.2
.0
.6
.7
0
,0
. 1
2
1
0
6
2
4
6
2
Transmis-
s ion Mi x
Shifts
O.O
1 .0
-O.2
0.5
-0.0
O.O
-0.3
0.0
-O.4
0.0
0.2
-0.2
-O. 1
O.O
1 .5
Engine
Mix
Shifts
O.3
O.3
-1 .5
0.7
-0.2
0.0
-1.1
0.6
O.9
0.5
-0.8
0.2
O.O
0.3
-8.7
Weight
Shifts
O
0
O
0
-o
O
O.
-7 .
O
0.
3.
9.
-5.
O.
0.
.O
.O
.7
.7
.O
.O
.4
2
O
,O
8
6
4
3
3
Al 1
Changes
Comb i ned
O
o
1
1
-o.
o
- 1 .
-7 .
O.
O.
1 .
9.
-5.
- 1 .
-6.
.6
. 3
.6
, 1
.3
.0
2
8
3
5
5
4
9
O
9
1979F
Car
SwMPG
2O
27
23
21
21 ,
14 ,
24.
27.
29.
1 1 .
28.
34.
31 .
23.
31 .
.9
.6
.2
.6
,2
.2
.4
7
1
1
1 t\j
O
6 '
2
6
9
3
FLEET
24.4
-0.2
0.3
-0.5
-0.4
-0.8
24. 1
-------
Table 12
Allocation of Fuel Economy Changes from 198OD to 1980F
for Subcompact Passenger Cars
Percent Fuel Economy Change due to
Manufacturer
American Motors
Chrysler Corp.
Ford Motor Co.
General Motors
BMW
Mercedes-Benz
F i at-Lanc-Frar i
Honda
Jag-Rov-Tr i
Nissan (Datsun)
Mitsubishi
Mazda
Toyota
VW-Audi -Porsche
Subaru
198OD
Car
SwMPG
22
26
25
23
26
18
24
26
15
32
31
31
26
32
29
.8
.8
.2
.5
. i
.3
.8
.9
. 1
.0
.7
.5
.6
.2
. 1
Powertraln
Opt imi -
zat ion
-O
1
-2
-O
O
O.
-1.
-O.
-0.
-1 .
0.
O.
1 .
-0.
3 .
.7
.2
. 1
.9
.O
,O
.9
. 1
.9
3
3
0
6
5
9
Transmi s-
s ion Mix
Shifts
O.O
-O. 1
0.2
O. 1
O. 1
0.0
0.6
0.6
O.O
-0.5
0. 1
0.3
1 . 7
O.2
O.O
Engine
Mix
Shifts
O. 1
O.O
0.6
-0. 1
O.O
O.O
-2.2
-O.O
0.0
O.6
0.2
O. 1
2.O
1 . 1
-0. 1
Weight
Mix
Shifts
-O
-0
1
4
1
O
1
O
-4
1
4
-6
-2
1
-3.
.6
.2
.7
.O
.O
.O
.3
.O
.9
.6
.2
.3
. 1
.7
. 2
Al 1
Changes
Combined
- 1
O
0
3
1
O
-2
O
-5
0.
4 .
-6.
3 .
2 .
O.
. 1
.9
.4
.O
. 1
O
.3
5
.7
.4
.7
O
.2
5
5
1980F
Car
SwMPG
22
27
25
24
26
18
24
27
14
32
33
29
27
33
29
.6
.O
.3
.2
.4
.3
.3
1
. 1 M
.2 ^
. 1
.2
.6
.4
.O
.3
FLEET
26.2
-0.5
0.3
0.4
3.2
3.4
27 . 1
-------
Table 13
Allocation of Fuel Economy Changes from 1981D to 1981F
for Subcompact Passenger Cars
Percent Fuel Economy Change due to
Manufacturer
Chrysler Corp.
Ford Motor Co.
General Motors
BMW
Mercedes-Benz
F iat-Lanc-Frar i
Honda
Isuzu
Nissan (Datsun)
Mi tsublshi
Mazda
Toyota
Subaru
1981D
Car
SwMPG
3O
25
26
27
19
25
28.
3O.
32
31 .
34.
3O.
31 .
.3
.O
. 3
.3
. 7
.0
.0
.0
.5
7
5
O
4
Powertrain
Opt iml -
zat ion
2
-1
- 1
O
-O
4
-O
-o
-1
O
-O
- 1
3
.5
.8
.8
.O
.3
.3
. 1
.6
. 1
.O
.4
.0
.2
Transm i s-
slon Mix
Shifts
1
O
O
O
0
0
1
O
-O.
0.
1 .
-0.
-o.
.9
.3
. 1
.O
.0
.3
.5
.2
.7
5
.3
,4
.5
Engine
Mix
Shifts
-2
-2
-0
O.
0
-5
O.
15
O.
-0.
0.
0.
0.
.5
. 2
2
.O
.0
.0
. 1
9
.5
9
O
2
1
Weight
Mix
Shifts
- 1
0
2
-0
O
1
0
0
- 1
1
-3
2.
1 .
.2
.5
.3
.5
.O
. 1
.O
.2
. 4
. 3
. 2
.5
.8
Al 1
Changes
Comb ineci
O
-3
O
-O
-O
0
1 .
15
-2
0.
-2 .
1 .
4 .
.6
.2
.4
.5
.3
.5
.4
.7
. 7
9
4
3
7
1981F
Car
SwMPG
3O
24
26
27
19
25
28
34.
31
32 .
33.
3O.
32 .
.4
.2
.4
. 1
.6
. 1
.4
.7
.6
,O
7
4
8
FLEET
28.7
-0.8
0.2
-0.4
1 .6
O.5
28.8
-------
Table 14
Allocation of Fuel Economy Changes from 1978D to 1978F
for Midsize Passenger cars
Percent Fuel Economy Change due to
Manufacturer
American Motors
Chrysler Corp.
Ford Motor Co.
General Motors
Mercedes-Benz
FLEET
Table 15
1978D
Car
SwMPG
13.6
16.2
17.9
19.9
13.9
18.6
Powertrain
Opt imi-
zat ion
-O.4
-0.7
-0.8
-0. 1
-O. 1
-0.4
Al locat ion
Transml s-
s ion Mix
Shifts
O.O
0.0
0. 1
O.O
O.O
O. 1
Engine
Mix
Shifts
O.O
-1.2
-0.1
0.6
-0. 1
O. 1
Weight
Mix
Shifts
O.O
1 .4
-0.4
-O. 1
0.0
-O.2
of Fuel Economy Changes from 1979D
for Midsize Passenger Cars
Percent Fuel
Manufacturer
Chrysler Corp.
Ford Motor Co.
General Motors
Mercedes-Benz
Saab
1979D
Car
SwMPG
18.4
17. O
2O. 1
13.9
O.O
Powertrain
Opt imi-
zat ion
-0.3
3.2
-0.5
-0. 1
0.0
Transmis-
s ion Mi x
Shifts
0.0
O. 1
0.0
O.O
O.O
Economy Change
Engine
Mix
Shifts
-0.5
O.9
-0.3
-2. 1
O.O
due to :
Weight
Mix
Shifts
2.2
O.2
0.0
O.O
0.0
Al 1
Changes
Comb ined
-O.4
-0.5
-1 .2
O.4
-O.3
-0.5
to 1979F
Al 1
Changes
Combined
1 . 4
4.3
-O.8
-2.2
0.0
1978F
Car
SwMPG
13.5
1.6.2
17.7
19.9
13.9
18.6
1979F
Car
SwMPG
18.7
17.8
2O. O
13.6
21.6
U>
I
FLEET
18.9
0.6
O.O
0.0
O.5
1 . 1
19. 1
-------
Table 16
Allocation of Fuel Economy Changes from 198OD to 198OF
for Midsize Passenger Cars
Percent Fuel Economy Change due to
Manufacturer
Chrysler Corp.
Ford Motor Co.
General Motors
Mercedes-Benz
Saab
FLEET
Table 17
1980D
Car
SwMPG
18.8
21.9
21.8
18.3
23. O
21.3
Powertraln
Opt imi -
zat ion
-1.3
-1 .0
-1.2
O.O
-0. 1
-1 .2
Al locat ion
Transmis- Engine
si on M ix Mix
Shifts Shifts
0.0
O. 1
O.O
0.0
0.7
O. 1
of Fuel
for
O.4
-O.4
1 .4
O.O
0.0
O.9
Weight
Mix
Shifts
3.2
2.2
O.2
0.0
O.O
1 .9
Economy Changes from 198 1D
Midsize Passenger Cars
Percent Fuel Economy Change
Manuf ac turer
Chrysler Corp.
Ford Motor Co.
General Motors
Mercedes-Benz
1981D
Car
SwMPG
24 .3
22.0
23 .4
19.5
Power tra In
Opt imi -
zat ion
-1.4
-2.0
-O.9
-O. 1
Transmis
s ion Mix
Shifts
O.2
-0. 1
-O.O
0.0
Engine
Mix
Shifts
0.3
-1.2
-O.2
O.O
due to :
Weight
Mix
Shifts
0.6
1 .4
-O.5
O.O
Al 1
Changes
Combined
2. 3
O.9
O.5
O.O
O.6
1 . 7
to 1981F
Al 1
Changes
Comb i ned
-0.2
-1.9
-1.6
-0. 1
198OF
Car
SwMPG
19.3
22. 1
21.9
18.3
23.2
21.6
1981F
Car
SwMPG
24. 3
21.6
23. 1
19.5
FLEET
23.3
-1 .2
O.O
-0.3
0. 1
-1.4
22.9
-------
-25-
Discussion of Allocation Results
Overall fleet fuel economy changes for all model years confirms
the previous finding using % DIFF, with the decrease in weight
accounting for most of the positive fuel economy changes.
Powertrain optimization is responsible for most of the negative
effects on fuel economy for all years but 1979. However, the
engine mix and weight mix gains cancel out these negative
effects. Shifts in the transmission mix at the fleet level has
no impact at all for within year fuel economy changes.
The two most notable within-year fuel economy increases by
manufacturer were the 1978 Peugeot fleet and the 1981 Isuzu
fleet. In both cases, new Diesel model types present in the
actual fleets were not present in these projected fleets, hence
are responsible for fuel economy increases of 16.9% and 15.7%
respectively, weight mix shifts, engine mix shifts or a
combination of the two were the major factors of within-year
fuel economy increases for most manufacturers, although six
manufacturers' within-year fuel economy increases were
attributed to positive shifts in powertrain optimization.
These include the 1978 Fiat and Isuzu fleets, the 1980 Subaru
fleet and the 1981 Mercedes-Benz, Fiat and Subaru fleets.
The most notable within year-fuel economy decrease was the 1979
Peugeot fleet, the influencing factor being an engine mix
shift. A closer look at sales shifts revealed actual gasoline
engine production was higher than projected. Nine
manufacturers had within-year fuel economy losses attributed
mainly to negative effects of powertrain optimization. These
include the 1978 Subaru fleet, the 1979 GM, Honda, Saab and
Toyota fleets, the 1980 GM, Saab and Subaru fleets and the 1981
Fiat and JRT fleets.
-------
-26-
The only manufacturer fleet where a transmission mix shift was
the major contribuing factor was the 1978 Toyota fleet. This
is the result of higher actual automatic transmission
production than projected.
Allocation analysis results for the Subcompact class (see
Tables 10-13) were varied ranging from no within year fuel
economy change in 1978, a loss of about 1% in 1979, and fuel
economy gains in 1980 and 1981 respectively of 3.4% and 0.5%.
Weight mix shifts tend to be a major factor in both fuel
economy losses and gains for the Subcompact fleet.
Notable within-year manufacturer fuel economy increases include
the 1978 Nissan fleet, the 1979 Mitsubishi fleet and the 1981
Isuzu fleet. The first two increases are attributed to weight
mix shifts. The Isuzu fleet increase is due to the presence of
a new Diesel model type not included in pre-model year Isuzu
forecasts.
Within-year fuel economy decreases include the 1978 and 1979 VW
fleets and the 1979 Honda fleet. The VW losses are due to
sales shifts favoring gasoline-powered engines. The Honda loss
is attributed to a heavier average weight of their Subcompact
fleet.
The major factor influencing the Midsize fleet (see Tables
14-17) within-year change for 1978, 1979 and 1981 is powertrain
optimization. The 1980 Midsize fleet is most influenced by
weight mix shifts. No large fuel economy changes were evident
for any Midsize producer for the model years of interest.
-------
-27-
Conclusions
1. Neither overprojection nor underprojection of production
seem to affect fuel economy significantly at any level of
aggregation (the fleet, by manufacturer, car class). If a
manufacturer projects overall production incorrectly, the
actual production distribution among MPG values within a
manufacturer product line seems to stay relatively the
same, keeping overall average MPG relatively constant for
individual manufacturers. The fleet MPG can still be
affected by the projected vs. actual mix among
manufacurers, however.
2. Overall fuel economy based on the final fleets was higher
than that of the projected fleets for all model years 1978
through 1981. The opposite seems to be true for model year
1982.
Recommendat ions
1. When the 1982 and 1983 final CAFE's data are available, the
allocation program should be run to detect any within year
fuel economy changes.
2. The mid-year CAFE estimates received by DOT from the
manufacturers should be acquired to provide improved data
bases (compared to the pre-model year forecasts) in the
long interval awaiting final CAFE data.
-------
-28-
References
1. "Fuel Economy Labeling and the Corporate Average Fuel
Economy (CAFE) Data Base, Proposed Improvments," Federal
Register, Vol. 45, No. 190, Monday, September 29, 1980, pp.
64540-64544.
2. "Refinement of Allocation Program," Memo, Karl H. Hellman
to Charles L. Gray, dated January 18, 1983.
3. "Fuel Economy of Motor Vehicles", Manual of Federal
Regulations; Title 40 - Part 600.
-------
A-l
Appendix A
Quick-look at Model Year 1982:
A change in the Projected-to-Actual pattern?
The body of this report concentrated on model years 1978-1981
because Final CAFE data for 1982 are essentially nonexistent.
"Midyear" estimates submitted to DOT by the manufacturers in
the summer of 1982 have been received and examined, however.
Since these updates are very near the end of the model year, it
would appear that they should closely resemble the Final CAFE
figures.
Figure A-l illustrates the comparison between Final and Midyear
manufacturers' fleet MPG values. It does indeed show that 80
percent of the available manufacturers' Midyear estimates for
1979, 1980 and 1981 were within + 0.5 MPG of their Final CAFE
figures. On an MPG basis, therefore, the Midyear estimates
have been a very good approximation of Final CAFE results.
Figure A-2 plots Final production volumes against Midyear
estimate volumes. (These are transformations of the actual
figures, to conceal manufacturer identities.) The plot shows
that 85 percent of the Midyear production estimates have been
within +_ ten percent of Final production volumes. Clearly
then, the Midyear estimates are a good approximation of Final
production volumes also.
Having shown that, for all practical purposes, Midyear = Final,
it is valid to compare 1982 Midyear results to 1982
projections, in tne same way that the earlier years' Final
figures were compared to their projections.
-------
A-2
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-
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._
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--
-
7
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-
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-
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7
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-
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-
^.
-
-
-
20 25 30
55
Midyear Estimate MPG
1979 O1980 X 1981
Figure A-l
Filial CAFE fuel economy vs. Midyear estimate
-------
0)
c
O
H
-P
O
A-3
j&A
£:.
w
PM
<
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Midyear Estimate Production Volume
1979 O1980 * 1981
Figure A-2
Final CAFE production volume vs. Midyear estimate
-------
A-4
Figure A-3 is the result, using the now extended 1978-1982^ data
base. Plotting the ratio of actual-to- projected MPG
vertically and the ratio of actual-to-projected production
volume horizontally, four quadrants are defined as follows:
1. Upper right - MPG and volume were both underestimated;
2. Lower right - MPG overestimated, volume underestimated;
3. Lower left - MPG and volume both overestimated; and
4. Upper left - MPG underestimated, volume overestimated.
In Figure A-3, open circles denote 1978 through 1981 data, and
filled circles denote 1982 data. Obviously, something changed
in 1982, as illustrated by Table A-l. This is a count, by
quadrant of Figure A-3, of the manufacturer forecasting track
record. The quadrant that the overall fleet data falls into is
also shown in this table, as a darkened box.
Conclusions are:
o For a majority of the manufacturers, and for the fleet,
production volumes have been QVERprojected consistently
from 1979 through 1982.
o For a majority of the manufacturers, and for the fleet,
MPG was UNDERprojected consistently from 1978 through 1981.
o In 1982, however, MPG was OVERprojected for a majority of
the manufacturers and for the fleet.
-------
O = 1978-81 Projected MPG
= 1982
^] = Fleet
MPG UNDERestimated
Production OVERestimated
O
0
OB]
0 C
0 0
0 00 OOIZJ
o o o o olzH
.2 .4 .6 .8 OOd!
O * °
o m 9 o
o * oO °
-
* 0
o c
MPG OVERestimated
Production OVERestimated
"
O
.1.15
1.10
O
-1.05
0
X>
o
-------
Table A-l
Sales and MPG forecasting Track Record, 1978-1982
Underprojected Sales Underprojected Sales Overprojected Overprojected Sales
Underprojected MPG Overprojected MPG Both Underprojected MPG
1978 Manufacturers
Fleet
45%
25%
10%
20%
1979 Manufacturers
Fleet
15%
25%
20%
40%
1980 Manufacturers
Fleet
39%
6%
28%
28%
CT>
1981 Manufacturers
Fleet
35%
12%
35%
18%
1982 Manufacturers
Fleet
20%
10%
60%
10%
-------
B-l
APPENDIX B
Calculation Methodology for
Fuel Economy Change Allocation
The procedure for computing fleet fuel econ-
omy changes due to specific factors, such as sys-
tem optimization and weight mix shifts, involves
the construction of matched sets of data from a
base fleet (e.g. 1978) and a new fleet (e.g. 1979),
and calculation of intermediate sales-weighted
fleet fuel economy values for the matched sets.
Depending on the degree of matching, the data sets
being compared include only certain known changes
between the sets, and hence the calculated inter-
mediate fleet MPG values reflect the fuel economy
effects of only those specific changes in fleet
makeup.
CALCULATION OF DIFFERENCES DUE TO SYSTEM
OPTIMIZATION: To determine the differences in
fuel economy between the 1978 and 1979 cars due
to system optimization, it was necessary to limit
the comparison to nominally identical vehicles.
For each manufacturer it was established which
1978 and 1979 models were identical in terms of
weight, displacement, and transmission type. When
this was established a new set of sales fractions
was calculated, based on 1978 sales estimates,
using only those combinations which were carried
over from 1978 to 1979. Two sales-weighted fuel
economy values were calculated using equation (2)
[see text]: one calculation using 1978 model MPG
values and 1978 carryover sales fractions, and
one using the 1978 model MPG values, also with
1978 carryover sales fractions. The difference
between the two values reflects the change in
fuel economy due to what we have called system
optimization. Since the weights, displacements,
transmissions - and their sales distributions -
are matched, any difference in fuel economy is
due to other factors. The main factors which
could be contributing to such a system optimiza-
tion change in fuel economy are:
Emission control system design changes;
Engine design and/or calibration changes;
Changes in transmission efficiency, shift
scheduling, or gear ratios;
Axle ratio changes;
Changes in test procedure which influence
fuel economy.
DIFFERENCES DUE TO TRANSMISSION MIX SHIFTS:
In the analysis of fuel economy changes due to
. system optimization, any IW/CID/transmission
combination not common to both years was eliminated
from consideration, and the sales distribution
of those combinations that were carried over was
held at the 1978 mix. If the calculation is re-
peated using only weight/displacement combinations
as the determinants for model year carryover, those
IW/CID/transmission combinations that are not common
to both sets of data are not "sifted out", but re-
main in their respective data bases; also, each of
the data bases retains its own sales split between
automatics and manuals within the carryover IW/CID
combinations.
Again, two SWMPG values are calculated using
equation 2, wherein the first MPG. is the harmonic
mean sales-weighted fuel economy of each manufac-
turer's 1978 models in IW/CID class i, and the
second MPG is the fuel economy of his 1979 models
in IW/CID class i. Both of these SWMPG values are
based on the same mix of the IW/CID classes (the
1978 mix), so the difference between the two is
due to system optimization plus all changes in
transmission mix.
DIFFERENCES DUE TO ENGINE MIX SHIFTS: Simi-
larly, by sifting for carryover at only the weight
class level, all differences in the IW/CID struc-
tures of the fleets are allowed to remain. The
difference between the two SWMPG values calculated
on this basis is thus due to system optimization,
transmission mix shifts, and shifts in the mix of
engine displacements*.
DIFFERENCES DUE TO WEIGHT MIX SHIFTS: The
bottom-line SWMPG values calculated from the full,
unperturbed data bases, each with its own sales
mix, includes all of the above effects plus the
effect of non-carryover weight classes and the
1979 redistribution of. sales among carryover
weight classes.
Table B-l summarizes the above calculation
methodology, and Figure B-l shows a diagram of the
relationship between the various calculated SWMPG
values. Since the methodology is suitable for a
comparison between any two vehicle sets (49-states
vs. California, cars vs. trucks, manufacturer X
vs. Y, etc.), Table B-l and Figure B-l are notated
for the general case rather than the year-to-year
case.
Table B-2 illustrates the equations for sep-
aration of individual factors from the combined
effects discussed above.
* This also includes shifts in the mix of engine
standards/systems; Fed vs. Cal. and Spark vs.
Diesel.
-------
B-2
table B-l - Method for Constructing Fuel Economy
Comparisons between Two Vehicle Groups
Cooligura t ion
Determinants
IW/CID/Trans-
nission Type
Vehicle Group "A"
Vehicle Group "B"
MPG Sales Fleet MPG Sales Fleet
Base(mpg-t) Base(f^) SWMPG Base(mpg<) Base(f^) SWMPG A-to-B SWMPG Change Attributed To:
FEg^ICT System optimization in carryover
I/C/T combinations
IW/CID
A *
Above plus new/discontinued I/C/T
combinations plus shifts in trans-
mission mix vithin carryover I/C
combinations
IW
A **
Above plus new/discontinued I/C
combinations plus shifts in engine
mix within carryover IW classes
Open
B *** FE
BB
Above plus new/discontinued IW
classes plus shifts in IW nix
among carryover IW classes
Includes B mix of transmissions
within c/o 1C classes.
Includes B mix of CT combinations
within c/o weight classes.
Includes B mix of all ICT combinations
in group B.
Discontinued
ICT combinations
Discontinued
wt. classes
system optimization __
New ICT combinations
and T mix shifts within
c/o 1C combinations
system optimization
plus net T changes
Discontinued
1C combinations
system optimization
plus net T changes
plus nee C changes
New 1C combinations
and C mix shifts within
c/o wt. classes .
New weights and wt. mix shifts
among c/o wt. classes
All changes combined
F-tg. 8-) - Re£otu7H4/Up6 between SWMPG ua£uea [nam tabte. B-J
-------
B-3
Table B-2 - Isolation of Specific Factors
Causing Fuel Economy Change
Percent Change In
Fuel Economy Due To:
Systems Optimization
Calculated By:
[/
[\ FEMICT
-']
x 100
Transmission Mix Shifts
^ FEBAICT\
A
x 100
Engine Mix Shifts
[/
[\ FEAA1 ' FEM1C
)-]
x 100
Weight Mix Shifts
FEBAI
FEAAl
x 100
All Changes Combined
x 100
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