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Frequently Asked Questions

About This Site

What is is federal government website that helps consumers make informed fuel economy choices when purchasing a vehicle and helps them achieve the best fuel economy possible from the cars they own. is maintained by the U.S. Department of Energy's (DOE's) Office of Energy Efficiency and Renewable Energy with data provided by the U.S. Environmental Protection Agency (EPA). The site helps fulfill DOE and EPA's responsibility under the Energy Policy Act of 1992 to provide accurate fuel economy information to consumers.

Fuel Economy Estimates

How are fuel economy ratings determined?

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.

Why does my fuel economy differ from EPA estimates?

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.

What should I do if my fuel economy is excessively low?

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

Why don't you have ratings for large vans, pickup trucks and SUVs?

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?

How are vehicle size classes defined?

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.

Vehicle Size Classes Used in the Fuel Economy Guide
Class Passenger & Cargo Volume (Cu. Ft.)
Two-Seaters Any (cars designed to seat only two adults)
  Minicompact < 85
  Subcompact 85 to 99
  Compact 100 to 109
  Mid-Size 110 to 119
  Large 120 or more
Station Wagons
  Small < 130
  Mid-Size 130 to 159
  Large 160 or more
Class Gross Vehicle Weight Rating (GVWR)*
Pickup Trucks Through 2007 As of 2008
  Small < 4,500 lbs. < 6,000 lbs.
  Standard 4,500 to 8,500 lbs. 6,000 to 8,500 lbs.
Vans Through 2010 As of 2011
  Passenger < 8,500 lbs. < 10,000 lbs.
  Cargo < 8,500 lbs.
Minivans < 8,500 lbs.
SUVs Through 2010 2011–12
  All < 8,500 lbs. < 10,000 lbs.
  As of 2013
  Small < 6,000 lbs.
  Standard 6,000 to 9,999 lbs.
Special Purpose Vehicles Through 2010 As of 2011
< 8,500 lbs. < 8,500 lbs.
or < 10,000,
depending on configuration

*Gross Vehicle Weight Rating (GVWR) is calculated as truck weight plus carrying capacity.

Where can I find more information about Corporate Average Fuel Economy (CAFE)?

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.

Do EPA fuel economy estimates account for the use of ethanol blends that are common today?

EPA's test fuel does not currently contain any ethanol or other oxygenates, but EPA does adjust their estimates to account for the impact of low-level ethanol blends. Ethanol contains about one-third less energy per gallon than gasoline. So, a car operating on 10% ethanol would achieve about 3% lower fuel economy than it would on 100% gasoline. EPA currently reduces all fuel economy test values by about 10% to account for ethanol in gasoline and other factors such as wind, hills, and road conditions.

Later this decade, EPA is phasing-in a requirement to change our federal emissions test fuel to include 10% ethanol by volume.

For more on EPA fuel economy tests, visit Questions and Answers: Fuel Economy Testing and LabelingAdobe Acrobat Icon.

Why don't EPA fuel economy tests use ethanol-blended gasoline now that most gasoline contains ethanol?

Later this decade, EPA is phasing-in a requirement to change our federal emissions test fuel to include 10% ethanol by volume.

For more on EPA fuel economy tests, visit Questions and Answers: Fuel Economy Testing and LabelingAdobe Acrobat Icon.

How is range determined for electric vehicles?

Electric vehicles are run through each test cycle until the battery charge decreases until it cannot follow the test cycle. The resulting distances are then weighted and adjusted to generate an overall range. It should be noted that range cannot be calculated based on fuel economy and battery capacity since manufacturers do not generally design vehicles to use the entire battery capacity. For more information, see EPA Test Procedures for Electric Vehicles and Plug-in HybridsAdobe Acrobat Icon.

In estimating electric vehicle fuel economy, is electricity use measured from the battery or from the charge source?

Electricity use is measured from the charge source. This is useful to consumers because (1) a small amount of energy is lost in charging the vehicle, and (2) this estimate represents the energy that is paid for by the consumer. As with other fuel types, upstream energy use and losses are not included in these estimates. For more information, see EPA Test Procedures for Electric Vehicles and Plug-in HybridsAdobe Acrobat Icon.

What is the average fuel economy of vehicles in the U.S.?

Production-weighted average fuel economy for 2016 model year vehicles was 29.0 mpg for cars, 21.4 mpg for trucks, and 25.6 mpg for light-duty cars and trucks combined. Today's passenger vehicles are nearly twice as efficient, on average, as those from 1975.

Source: EPA. 2016. Light-Duty Automotive Technology, Carbon Dioxide Emissions, and Fuel Economy Trends: 1975 Through 2016 (EPA-420-R-16-01)Adobe Acrobat Icon, Tables 2.1, 3.4.1, and 3.4.2.

Fuels and Fuel Prices

What does gasoline cost?

Links to information on the cost of gasoline in the United States can be found in the Gasoline Prices section.

Should I use regular or premium gasoline?

Our page on selecting the right octane fuel can help you select the right grade of fuel for your vehicle.

Where does gasoline from my local station come from?

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.

Where can I buy E85, biodiesel, or other alternative fuels?

The Alternative Fuels Data Center's Alternative Fueling Station Locator can help you find alternative fueling stations in your area.

Tax Incentives and Disincentives

Are federal tax incentives available for any vehicles?

Yes. Qualifying all-electric and plug-in hybrid vehicles purchased in or after 2010 may be eligible for a federal income tax credit of up to $7,500. The credit amount will vary based on the capacity of the battery used to power the vehicle. State and/or local incentives may also apply.

What is the Gas Guzzler Tax?

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.

Gas Guzzler Tax
Unadjusted MPG
(city/highway combined)
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


How are total annual greenhouse gas emissions estimated?

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.