Frequently Asked Questions
Fuel Economy Estimates
EPA estimates are based on laboratory tests conducted by manufacturers according to federal regulations. EPA re-tests about 10% of vehicle models to confirm manufacturer's results. For more detailed information, visit our page on How Vehicles Are Tested.
No test can accurately predict fuel economy for all drivers and all driving conditions. Driver behavior, driving conditions, vehicle maintenance, fuel characteristics, weather, and other factors can all affect fuel economy significantly as explained here.
If your fuel economy is excessively low, your vehicle may need to be serviced or repaired. You may want to contact your dealer or a reputable repair facility to check your vehicle. The following are some of the diagnostic checks a mechanic will typically conduct for poor fuel economy:
- Perform "On-Board Diagnostic System Check" for diagnostic trouble codes (sensors or actuators which may be malfunctioning)
- Check for dragging brakes
- Check transmission shift patterns for slipping, use of all gears, lock-up operation
- Check ignition timing
- Check owner's driving habits including A/C usage, hard accelerations, carrying heavy loads
- Check emission control system
- Check vacuum hoses for leaks, kinks, proper routing
- Check tire pressure
- Check fuel type, quality, and alcohol content
- Check fuel pressure and fuel system for leaks
- Check air cleaner element
- Check coolant level
- Check ignition system for wet plugs, cracks, wear, improper gap, burned electrodes, or heavy deposits, cracking or improperly connected ignition wires
- Check for proper calibration of speedometer
- In extreme cases, there may be engine problems such as poor compression or faulty fuel injectors
Vans, pickup trucks, and sport utility vehicles (SUVs) weighing more than 8,500 pounds gross vehicle weight are classified as heavy-duty vehicles. Fuel economy regulations do not apply to these vehicles, so they are not tested. Additional information is available at Which Vehicles Are Tested?
The size class for cars is based on interior passenger and cargo volumes as described below. The size class for trucks is defined by the gross vehicle weight rating (GVWR), which is the weight of the vehicle and its carrying capacity. Fuel economy regulations do not apply to heavy-duty vehicles, so they are not tested. See Which Vehicles Are Tested for more information on these vehicles.
|Class||Passenger & Cargo Volume (Cu. Ft.)|
|Two-Seaters||Any (cars designed to seat only two adults)|
|Minicompact||Less than 85|
|Subcompact||85 to 99|
|Compact||100 to 109|
|Mid-Size||110 to 119|
|Large||120 or more|
|Small||Less than 130|
|Mid-Size||130 to 159|
|Large||160 or more|
|Class||Gross Vehicle Weight Rating (GVWR)*|
|Pickup Trucks||Through 2007||Beginning 2008|
|Small||Less than 4,500 lbs.||Less than 6,000 lbs.|
|Standard||4,500 to 8,500 lbs.||6,000 to 8,500 lbs.|
|Vans||Through 2010||Beginning 2011|
|Passenger||Less than 8,500 lbs.||Less than 10,000 lbs.|
|Cargo||Less than 8,500 lbs.|
|Minivans||Less than 8,500 lbs.|
|Sport Utility Vehicles|
|All||Less than 8,500 lbs.||Less than 10,000 lbs.|
|Small||Less than 6,000 lbs.|
|Standard||6,000 to 9,999 lbs.|
|Special Purpose Vehicles||Through 2010||Beginning 2011|
|Less than 8,500 lbs.||Less than 8,500 lbs.
or less than 10,000,
depending on configuration
*Gross Vehicle Weight Rating (GVWR) is calculated as truck weight plus carrying capacity.
First enacted by Congress in 1975, the purpose of CAFE is to reduce energy consumption by increasing the fuel economy of cars and light trucks. Information on CAFE is available from the National Highway Traffic Safety Administration.
No. The EPA fuel economy tests use 100 percent gasoline, and no adjustments are made to account for ethanol. Most conventional vehicles using E10 (10 percent ethanol) will experience a 3 to 4 percent reduction in fuel economy.
EPA fuel economy tests are conducted according to Federal testing regulations which require 100 percent gasoline. These regulations could be changed, but changing them would be somewhat problematic. While it is common for gasoline pumps to allow for up to 10 percent ethanol, the actual amount of ethanol blended into the gasoline varies greatly, and fuel blending requirements vary by state. Changing the test methods would also make it difficult to compare vehicles tested with ethanol blends with those tested with straight gasoline. So, without a national standard for blended regular gasoline and a Federal mandate to change the test fuel used, the EPA will not change the test fuel.
Average fuel economy for 2013 model year vehicles is 27.4 mpg for cars, 19.7 mpg for trucks, and 24 mpg for light-duty cars and trucks combined. Today's passenger vehicles are nearly twice as efficient, on average, as they were in 1975.
Fuels and Fuel Prices
Links to information on the cost of gasoline in the United States can be found in the Gasoline Prices section.
The Federal Trade Commission's page, Facts for Consumers, answers this and other questions about octane ratings, fuel grades, and choosing the right fuel for your vehicle.
The Department of Energy does not collect data on the source of gasoline sold at gas stations. However, they do provide a Primer on Gasoline Sources and Markets that explains why this is difficult to determine.
The Alternative Fuels Data Center's Alternative Fueling Station Locator can help you find alternative fueling stations in your area.
Tax Incentives and Disincentives
Fueleconomy.gov's Tax Information Center provides tax incentive information for
|At least 22.5||$0|
|At least 21.5, but less than 22.5||$1,000|
|At least 20.5, but less than 21.5||$1,300|
|At least 19.5, but less than 20.5||$1,700|
|At least 18.5, but less than 19.5||$2,100|
|At least 17.5, but less than 18.5||$2,600|
|At least 16.5, but less than 17.5||$3,000|
|At least 15.5, but less than 16.5||$3,700|
|At least 14.5, but less than 15.5||$4,500|
|At least 13.5, but less than 14.5||$5,400|
|At least 12.5, but less than 13.5||$6,400|
|Less than 12.5||$7,700|
The Energy Tax Act of 1978 established a Gas Guzzler Tax on the sale of new cars with particularly poor fuel economy to discourage the production of such vehicles—trucks are exempt. It is collected directly from the manufacturer rather than the buyer. The amount paid by the manufacturer is disclosed on the automobile's fuel economy label (the window sticker on new cars).
The fuel economy figures used to determine the Gas Guzzler Tax are different from the fuel economy values provided on this web site and in the Fuel Economy Guide. The tax does not depend on the actual on-the-road fuel economy, which may be more or less than the EPA published value for some drivers.
The greenhouse gas estimates presented here are full fuel-cycle estimates, combining the three major greenhouse gases emitted by motor vehicles:
- Carbon dioxide (CO2)
- Nitrous oxide (NOx)
- Methane (CH4)
Full fuel-cycle estimates include all steps in the use of a fuel, from production and refining to distribution and final use. This gives a more complete picture of the climate change impacts of using a particular fuel.
Some greenhouse gases have greater impacts on climate than others. Scientists have developed relative global warming potential numbers for each gas that gives its impact on global climate relative to that of carbon dioxide. We use the global warming potentials developed by the Intergovernmental Panel on Climate Change to combine the three gases into tons of carbon dioxide equivalent. We believe this gives the most complete and accurate reflection of the impact of each vehicle's energy use on the global climate.
Numerous assumptions and calculations are necessary to estimate full fuel-cycle greenhouse gas emissions in carbon dioxide equivalents. So, estimates from different sources will vary. Our estimates are taken from the U.S. Department of Energy's GREET Model developed by Argonne National Laboratory.