EPA - Office of Mobile Sources                                    EPA420-F-95-003
Technical Overview                                            August 1995
     FUEL  ECONOMY IMPACT ANALYSIS OF RFG
     The Environmental Protection Agency (EPA) evaluated fuel economy impacts
      of reformulated gasoline (RFG) using a number of reliable studies (including
      the $40 million joint research program by the auto and oil industries)
      involving approximately 4000 individual observations.

     EPA found that the use of oxygenated fuels and RFG causes a small decrease
      (l-3%) in fuel economy.

     EPA determined that a vehicle's fuel economy depends on the energy content
      of the gasoline on which it runs. This conclusion matches what would be
      expected based on combustion theory.

     This determination is also supported by similar conclusions drawn by
      industry through their own studies (both laboratory and on-road testing).

     Therefore, the following points focus on energy content more than fuel
      economy. The impact of fuel changes on fuel economy should be very similar
      to the impact of fuel changes on the energy content.

Conventional Gasoline

     It is important to note that the energy content of gasolines varies from season
      to season. The table below shows that typical summer conventional gasolines
      contain 1.7% more energy than typical winter conventional gasolines.

      Average Energy Content (btu per gallon)
      Summer          Winter                 Difference

      114,500          112,500                 1.7%

     The energy content of conventional gasolines also varies widely from batch to
      batch and station to station.  The table below shows this variation within
      each season.

                 Energy Content (btu per gallon)
                 Minimum        Maximum        Difference

      Summer    113,000          117,000          3.4%
      Winter     108,500          114,000          5.0%

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Technical Overview                                                         Page 2
Conventional Gasoline vs RFG

     A gallon of RFG contains about 1-3% less energy than a gallon of
      conventional gasoline. This difference is considerably smaller than the
      differences in energy content among conventional gasolines described above.

     RFG contains oxygenates, which contain less energy per unit volume than
      conventional gasoline. The table below outlines the differences in energy
      content between RFG and conventional gasoline based on the three most
      widely used oxygenates.
Oxygenate
Ethanol
ETBE
MTBE
Energy
Content of
Oxygenate
(btu/gallon)
76,100
96,900
93,500
Volume
of Oxy-
genate
in RFG
5.71%
12.8%
11.0%
Energy
Content
of RFG
(btu/gallon)*
111,836
111,811
111,745
Difference in
Energy Content
(RFG vs
Conventional)
1.9%
1.9%
2.0%
      Assumes base gasoline has energy content of 114,000 btu/gallon

      Other than oxygenates, there are other minor differences between RFG and
      conventional gasoline that also impact the energy content of the fuel.  These
      impacts are different in summer and winter.

      Summer RFGs contain approximately 1.0% less energy than summer
      conventional gasolines.
            This is expected to reduce fuel economy on average by 1.0% during the
            summer.
            For example, a car that gets 25 miles per gallon with conventional
            gasoline may get 24.75 miles per gallon with RFG.

      Winter RFGs contain approximately 3.0% less energy per gallon than winter
      conventional gasolines.
            This is expected to reduce fuel economy on average by 3.0% during the
            winter.
            For example, a car that gets 25 miles per gallon with conventional
            gasoline may get 24.25 miles per gallon with RFG.

      A March 1995 study conducted in Wisconsin confirmed a 2.8% reduction in
      average fuel economy with winter RFG. This study used eight private
      vehicles of various makes, designs, and ages, four different retail gasolines

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Technical Overview                                                        Page 3


(including conventional and reformulated gasolines), and 12,800 miles of driving on
city streets.

Other Fuel Economy Factors

     While all analyses to date show RFG has a minimal direct effect on fuel
      economy, there are many other factors that can dramatically affect fuel
      economy. The table on page 4 outlines these factors and their potential
      impacts on fuel economy. The majority of these factors reduce fuel economy
      more than only the use of RFG.

     Drivers experiencing a consistent, drastic change in fuel economy (i.e.,
      reductions far greater than the expected 1-3%) that is not the result of the
      other mitigating factors described in the table on page 4, should consider
      that the reduction may be a maintenance problem or other issue unique  to
      the vehicle.

Fuel Economy and Pollution

     Common sense suggests  that the slight reduction in fuel economy from RFG
      would be associated with an increase in pollution. Fuel economy and
      pollutants emitted are not always directly related, however, because vehicles
      are designed to meet the emission standards on a basis of pollutant per mile.

     Hydrocarbon emissions and other pollutants such as carbon monoxide and
      oxides of nitrogen depend mainly on how much the vehicle is driven and how
      well the emission controls are functioning. There is little connection between
      these emissions and fuel consumption, although it is to some extent
      dependent on the circumstances causing the  difference in fuel economy.  If,
      for example, a vehicle suddenly experiences a dramatic change in its fuel
      economy due to something going wrong with the vehicle, there is likely to
      also be a significant impact on the vehicle's emission performance. But if
      that problem does not affect the vehicle's emission control system, then there
      may be little or no impact on emissions.

     On the other hand, carbon dioxide (C02) emissions are always linked to fuel
      consumption because C02 is the ultimate end product of burning gasoline.
      The more fuel a car burns, the more C02 it emits.

     For those situations where fuel economy changes merely as a result of driving
      habits, driving conditions, or fuel composition (as is the case with RFG),  and
      vehicle performance remains unaffected, the emission performance of the
      vehicle is also likely to remain unaffected.

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Technical Overview
Page 4
Effect
Temperature*
Head Wind
Hills/Mountains
Poor road
conditions*
Traffic Congestion
Highway speed
Acceleration rate
Wheel Alignment
Tire Type
Tire Pressure*
Air Conditioning
Defroster*
Idling/Warmup*
Windows
Conditions
20oFvs 77oF
20mph
7% road grade
Gravel, curves,
slush, snow, etc.
20 vs 27 mph
average speed
70 vs 55 mph
"Hard" vs "Easy"
1/2 inch
non-radial vs
radial
15 psi vs 26 psi
Extreme Heat
Extreme Use
Winter vs
Summer
Open vs Closed
Average Fuel
Economy
Reduction
5.3%
2.3%
1.9%
4.3%
10.6%
N/A
11.8%
<1%
<1%
3.3%
21%
Analogous to
A/C on some
vehicles
Variable with
Driver
Unknown but
likely small
Maximum Fuel
Economy
Reduction
13%
6%
25%
50%
15%
25%
20%
10%
4%
6%
N/A

20%


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* These factors, with their respective reduction in fuel energy content, can decrease fuel economy in
the winter season relative to summer by 20 percent or more independent of whether the RFG
program is in effect.

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