EPA/AA/CTAB/90-01
Technical Report
Downward Trend in Passenger Car
Fuel Economy— a View of Recent Data
by
J. Dillard Murrell
and
Robert M. Heavenrich
January 1990
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 and Radiation
Office of Mobile Sources
Emission Control Technology Division
Control Technology and Applications Branch
2565 Plymouth Road
Ann Arbor, Michigan 48105
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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
ANN ARBOR. MICHIGAN 48105
OFFICE OF
AIR AND RADIATION
MEMORANDUM
SUBJECT: Exemption From Peer and Administrative Review
FROM:
Karl H. Hellman, Chief
Control Technology and Applications Branch
TO:
Charles L. Gray, Jr., Director
Emission Control Technology Division
The attached report entitled "Downward Trend in Passenger
Car Fuel Economy—A View of Recent Data," (EPA/AA/CTAB/90-01),
is a brief analysis of the two-year trend in fuel economy from
model year 1988 to model year 1990, and where the data may
indicate fuel economy is headed.
Since this report is concerned only with the presentation
of data and its analysis and does not involve matters of policy
or regulations, your concurrence is requested to waive
administrative review according to the policy outlined in your
directive of April 22, 1982.
Concurrence
Date
Cha
ECTD
Nonconcurrence:
Date:
Charles L. Gray, Jr., Dir., ECTD
cc: E. Burger, ECTD
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Last year's technology and MPG trend report[l] noted an 0.4 MPG decline in average
passenger car fuel economy from 1988. Regarded as possibly just a one-time blip in
the curve, the decline was neither emphasized nor subjected to any close scrutiny.
The model year 1990 data is in, and it shows another decline in fuel economy— it
is now a two-year trend. If this backslide continues, problems with nationwide fuel
consumption will increase and global warming trends will worsen at a pace faster than
is generally being assumed by analysts. Thus it is appropriate to explore some of the
characteristics of, and causes for, of the downward MPG trend.
The data used for this report come from the auto manufacturers, and represent
their forecasts of production for the U.S. market. For the current model year and its
predecessor year (prior to finalization of the official data for. fuel economy
standards compliance), the data are furnished for, and used primarily for, the fuel
economy labeling and Gas Mileage Guide programs. The data are checked against
subsequent, but still pre-model-year, MPG and production volume figures furnished by
the manufacturers to the Department of Transportation and to the trade press, and
adjusted accordingly. All MPG figures herein are EPA combined city-highway, "55/45"
MPG; no on-road or test procedure correction factors have been applied to any of the
MPG data. Vehicle weights are "inertia weight," i.e. curb weight plus 300 Ibs.
Table 1 summarizes the two-year MPG decline for the passenger car fleet from 1988
to 1990, and the corresponding trends in vehicle weight and engine and acceleration
characteristics (to prevent inter-year changes in the sales mix among manufacturers
from distorting the comparison, the 1990 mix was also used with the 1988 data).
From 1988 to 1990, there was a 4% decline in MPG and a 6% weight gain; yet,
average zero-to-60 MPH acceleration time* continued to decrease, due to the 10%
increase in average engine horsepower. The horsepower increase is the result of a 7%
gain in average engine power density (HP per cubic inch) and a 4% rise in average
cubic inch displacement.
The fleet-level trends are mirrored directionally in all three of the major market
sectors (import figures include cars built in the U.S. by foreign companies, and cars
built overseas for sale by U.S. companies). Domestic cars, European cars, and Asian
cars all lost MPG, with Asian car MPG dropping at a rate at least double that of the
other two sectors. All three sectors gained weight, with Asian cars gaining it at a
rate more than double that of the other two. All three sectors boosted horsepower
(more than enough to offset their weight gain), with Asian cars increasing in average
horsepower at a rate three times that of the .Europeans and more than four times that
of the Domestics.
The method used to increase power differs from sector to sector: the Europeans'
power gain was due entirely to power density improvements, while the Domestics' and
Asians' power increases came by adding CID increases on top of HP/CID increases, in
about equal proportions. Asian cars' average CID is increasing by 5% a year, and
HP/CID even faster.
Given no more information than that the above parameters of concern are changing
in the same direction across all three market sectors, it could be inferred that all
manufacturers in each sector share/contribute equally in the sector's behavior.
However, only one or two high-selling manufacturers in a sector could be driving the
sector averages; hence it is pertinent to examine the data across the manufacturers
in each sector.
* estimated; see [2].
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Table 2 shows several aspects of the fuel economy trend, by manufacturer. The 22
manufacturers shown are the top-sellers; of the total projected 1990 sales, each
represents 0.1% or greater, and together they represent more than 98%. The upper part
of the table lists those with MPG declines between 1988 and 1990; the lower part
lists those four whose MPG did not drop in that interval.
The first numeric column in Table 2 shows the 1988 to 1990 MPG change for each
manufacturer: the eight greatest losses were posted by Asian companies, the Domestics
appear in the lower half of the upper (backsliding) group, and three of the four non-
backsliding manufacturers are European.
The second and third columns are reminders that MPG backsliding has been going on
for more than just the last two years. Comparing each manufacturer's 1990 MPG to its
highest average, whenever it occurred, all these companies except Yugo have lost MPG
to some degree; of the ten who have lost it in double figures, seven are Japanese,
three German. Some companies have a history of several consecutive years of MPG
backsliding.
The two rightmost columns give linear projections of the two-year MPG trend: if
the current rates of decline continue, 15 of the 18 backsliding manufacturers
(including all three Domestics) will drop below 25 MPG before the end of the decade;
the fleet will drop below 25 MPG by 1995.
Table 3 shows the 1988 to 1990 change in average weight by manufacturer. All
except BMW gained weight, and all who gained in double figures are Japanese. The
figures for Mitsubishi and Daewoo do not fit the pattern of other Asian companies.
Table 4 gives the two-year change in performance capability. All manufacturers in
double figures are Asian. Again, the Mitsubishi and Daewoo figures do not appear to
be typically "Asian". Ford is not on the performance-increase track of the other
Domestics.
The magnitudes of the horsepower increases in Table 5 are surprisingly large
compared to past trends. More than half the manufacturers are increasing their
average power in double figures; Asian manufacturers lead the power growth trend; in
fact, every Japanese manufacturer except Mitsubishi is increasing power in double
figures.
The two-year trends in engine specific power, Table 6. and engine displacement,
Table 7. follow the pattern seen above: where there are double-figure increases there
are Asian companies. Five of the six companies who held average CID constant, or
decreased it (Table 7), still gained in average power (Table 5) by improving power
density (Table 6).
Light-duty trucks have a downward trend in fuel economy too: see Table 8.
References
1. Heavenrich and Murrell, "Light Duty Automotive Technology and Fuel Economy Trends
Through 1989," Report EPA/AA/CTAB/89-04, May 1989.
2. Heavenrich, Murrell, and Cheng, "Light Duty Automotive Fuel Economy and Technology
Trends Through 1987," SAE Paper 871088, May 1987.
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Table 1
Two-year Trend: Percent Change, 1988 to 1990 Models
A. 55/45 MPG
B. Weight
C. 0-60 Time
D. Horsepower
E. Engine HP/CID
F. Engine CID
Fleet
-4
6
-4
10
7
4
Domestic
-3
4
-1
5
3
2
European
-2
4
-3
8
8
0
Asiz
-6
9
-9
22
11
10
Note: the 1988 figures use the 1990 mix of sales volumes by manufacturer.
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Table 2
Manufacturers Decreasing Their Average Fuel Economy
Manufacturer
Isuzu
Toyota
Subaru
Nissan
Diahatsu
Hyundai
NUMMI
Mazda
Honda
Chrysler
Volvo
Saab
VW-Audi
GM
Ford
Jaguar
Daewoo/GM
Suzuki
% Change in
Co.Avg.F.E.
1988 to 90
-9
-9
-9
-8
-8
-7
-6
~5
-4
-4
-4
-3
-3
-3
-2
-2
-2
-1
% Change in
Co.Avg.F.E.
Max. to 90
-13
-10
-9
-15
-8
-7
-10
-17
-13
-4
-7
-3
-16
-3
-3
-2
-2
-12
No. Consecu-
tive Years of -
MPG Decline L
3
2
2
7
2
4
2
2
2
Linear Projection:
Year to Drop Below:
30 MPG 25 MPG
1993
now
now
now
1997
1993
1993
now
1991
now
now
now
now
now
now
now
>2000
>2000
1996
1994
1993
1993
2000
1997
1998
1996
1999
1994
now
1991
1998
1995
1994
now
>2000
>2000
Manufacturers Not Decreasing
Their Average Fuel Economy
Manufacturer
Mitsubishi
Yugo
Mercedes
BMW
% Change in
Co.Avg.F.E.
1988 to 90
0
0
0
3
% Change in
Co.Avg.F.E.
Max, to 90
-8
0
-21
-19
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Table 3
Their Average Weight
Manufacturer
Subaru
Toyota
Suzuki
Isuzu
NUMMI
Nissan
Mazda
Chrysler
Diahatsu
Hyundai
Honda
VW-Audi
Mercedes
Volvo
Ford
Saab
GM
Mitsubishi
Daewoo/GM
Yugo
Jaguar
reasing
ight
% Change in
Avg. Weight
1988 to 90
16
13
12
11
10
9
8
8
8
7
5
5
5
4
4
3
3
2
2
1
1
Manufacturer Not Increasing
Its Average Weight
% Change in
Avg. Weight
Manufacturer 1988 to 90
BMW -1
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Table 4
Manufacturers Increasing
Their Acceleration Performance
Manufacturer
Nissan
Isuzu
NUMMI
Hyundai
Diahatsu
Jaguar
Subaru
BMW
Mazda
Volvo
Suzuki
GM
Honda
Saab
Daewoo/GM
Toyota
Chrysler .
% Change in
0-60 Time,
1988 to 90
-23
-18
-17
-16
-12
-8
-7
-6
-6
-6
-5
-5
-4
-4
-3
-3
-3
Manufacturers Not
Their Acceleration
Manufacturer
Yugo
VW-Audi
Mercedes
Mitsubishi
Ford
Increasing
Performance
% Change in
0-60 Time,
1988 to 90
0
0
0
3
8
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Table 5
Manufacturers Increasing
Manufacturer
Nissan
Isuzu
NUMMI
Hyundai
Diahatsu
Subaru
Suzuki
Toyota
Mazda
Volvo
Jaguar
Chrysler
Honda
GM
Saab
VW-Audi
Daewoo/GM
Mercedes
BMW
Yugo
easing
sepower
% Change in
Engine HP
1988 to 90
51
43
37
35
31
29
21
20
16
12
12
11
11
10
8
8
7
6
6
2
Manufacturers Not Increasing
Their Average Horsepower
% Change in
Engine HP
Manufacturer 1988 to 90
Mitsubishi -2
Ford -6
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Table 6
Manufacturers Increasing
Manufacturer
Isuzu
NUMMI
Nissan
Suzuki
Volvo
Mercedes
Hyundai
Diahatsu
Subaru
BMW
Toyota
Saab
GM
Mitsubishi
Chrysler
Honda
Mazda
Jaguar
VW-Audi
Daewoo/GM
asing
Density
% Change
inHP/CID
1988 to 90
39
37
23
18
13
13
13
11
10
10
8
8
8
7
6
5
5
4
3
1
Manufacturers Not Increasing
Their Engine Power Density
% Change
inHP/CID
Manufacturer 1988 to 90
Yugo 0
Ford -9
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Table?
Manufacturer
Nissan
Hyundai
Diahatsu
Subaru
Toyota
Mazda
Jaguar
Daewoo/GM
Honda
Chrysler
VW-Audi
Isuzu
Suzuki
Ford
Yugo
GM
reasing
lacement
% Change in
Engine CID
1988 to 90
23
20
18
17
11
11
7
6
5
5
4
3
3
2
2
1
Manufacturers Not Increasing
Their Engine Displacement
Manufacturer
Saab
NUMMI
Volvo
BMW
Mercedes
Mitsubishi
% Change in
Engine CID
1988 to 90
0
0
-1
-4
-6
-9
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Table 8
Three-year MPG Trend, Light Trucks:
Percent Change, 1987 to 1990 Models
% Change in
Avg. F.E.
1987 to 90
Fleet -1
Domestic 0
Chrysler 5
GM 3
Ford -6
Grumman -6
European 7
Volkswagen 11
Rover -1
Asian -10
Nissan 4
Suzuki -3
Mazda -6
Toyota -13
Mitsubishi -16
Isuzu -19
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Appendix
It is appropriate to show more detail for some specific cases to illustrate how
trends in some of these technical parameters are influenced. We have chosen two
cases where engine size and horsepower changes are noteworthy; the two cases are
Ford, whose overall results indicate a decrease in average power density (horsepower
per CID), and Nissan, who had the largest average horsepower increase.
The tables below show how changes in engine offerings and sales mix shifts among
them combine to produce changes in sales-weighted average values for CID and
horsepower and, correspondingly, power density. The Ford trend is a result of sales
shifts away from higher horsepower versions within each engine type. Nissan's trend
results from higher CID offerings, higher powered versions within them, and sales
shifts (both within and among the engines) toward higher power.
1988 Ford Engines:
1990 Ford Engines:
Cylinders
4
4
4
Avg.4
6
6
Avg.6
8
8
Avg.8
Co.Avg.
CID
113
140
152
129
182
231
206
302
351
303
201
Hp
Versions
81,84,90,108
96,98,100,
151,194
88
99
140
150
145
150,220
180
192
139
Cylinders
4
4
4
Avg.4
6
6
Avg.6
8
8
Avg.8
Co.Avg.
CID
113
140
152
132
182
231
209
302
351
304
206
Hp
Versions
84,90,108
96,98,100
88
95
140,220
120,140,210
140
150,225
180
162
130
1988 Nissan Engines:
1990 Nissan Engines:
Cylinders
4
4
4
Avg.4
6
Avg.6
CID
98
110
120
103
181
181
Hp
Versions
70
125
94,97,99
78
157,165,205
160
Cylinders CID
Co.Avg.
120
96
4
4
4
Avg.4
6
Avg.6
8
Co.Avg.
98
110
146
117
181
181
274
148
Hp
Versions
90
125
138,140
110
160,225,280
186
278
146
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