These misconceptions are based on user feedback to www.fueleconomy.gov and are listed in no particular order.
1. MYTH: You have to drive a small car to get good fuel economy.
FACT: Advanced technologies like electric and hybrid drivetrains, cylinder deactivation, direct fuel injection, turbocharging, advanced transmissions, low rolling resistance tires and aerodynamic designs are allowing standard-sized vehicles to be very fuel efficient. For the 2020 model year, more than half of the top ten most efficient vehicles (the list that excludes EVs and PHEVs) are midsized or large cars.
2. MYTH: Manual transmissions always get better fuel economy than automatics.
FACT: Advances in automatic transmissions have improved their efficiency to the point that the automatic version of a vehicle often gets the same or better fuel economy than the version with a manual transmission. For vehicles offered in both automatic and manual transmissions, consumers can easily compare fuel economy using our Find a Car feature.
3. MYTH: It takes more fuel to start a vehicle than it does to let it idle.
FACT: Modern fuel injected engines start very efficiently, especially when warmed up. Idling can use a quarter to a half gallon of fuel per hour—depending on your vehicle's engine size—costing you about 1 to 2 cents per minute. Turn off your engine when your vehicle is sitting still, except when you are waiting in traffic or waiting in a line where you would need to turn it on and off frequently.
4. MYTH: Vehicles need to warm up before they can be driven.
FACT: Modern vehicles can be driven within seconds of being started, though the engine should not be subjected to extreme loads until it has reached its normal operating temperature. Plus, the quickest way to warm up a vehicle's engine is to drive it.
5. MYTH: As a vehicle ages, its fuel economy decreases significantly.
FACT: A vehicle that is properly maintained will retain its efficiency for many years. The EPA tests vehicles with about 5,000 miles on the odometer to account for the break-in period since a vehicle's fuel economy will typically continue to improve over the first several years of ownership. Vehicles that are 10 or even 15 years old will experience little decrease in fuel economy if properly maintained.
6. MYTH: Replacing your air filter will help your car run more efficiently.
FACT: This is true for older vehicles with carbureted engines, but modern fuel-injected engines have on-board computers that automatically adjust the fuel-air ratio to the proper level. Changing a dirty air filter won't increase your fuel economy, but it might improve your engine's performance.
7. MYTH: Aftermarket additives and devices can dramatically improve your fuel economy.
FACT: Excluding full conversions that meet all EPA certification standards, tests have shown that such devices and additives do not improve fuel economy and may damage your engine and/or increase your tailpipe emissions. For further information, see "Gas-Saving Products: Fact or Fuelishness?" by the Federal Trade Commission.
8. MYTH: Using premium fuel improves fuel economy.
FACT: Unless your vehicle was specifically designed for premium fuel, knocks severely with regular fuel or is used in severe duty operation, you will probably experience little or no benefit from using premium fuel over regular. Consult your owner's manual to see whether premium is recommended and under what conditions (e.g., towing). Find more information about selecting the right octane.
9. MYTH: The EPA fuel economy estimates are a government guarantee on what fuel economy each vehicle will deliver.
FACT: The primary purpose of EPA fuel economy estimates is to provide consumers with a uniform, unbiased way of comparing the relative efficiency of vehicles. Even though the EPA's test procedures are designed to reflect real-world driving conditions, no single test can accurately model all driving styles and environments. Differing fuel blends will also affect fuel economy. The use of gasoline with 10% ethanol can decrease fuel economy by about 3% due to its lower energy density.
10. MYTH: All vehicles are tested for fuel economy.
FACT: Current testing regulations only require vehicles below a given gross vehicle weight rating (GVWR) to be tested. Light-duty passenger vehicles with a GVWR of 10,000 lbs. or less are tested as well as pickup trucks and cargo vans with a GVWR of 8,500 lbs. or less. Several popular models, such as the Ford F250/350, Chevrolet/GMC 2500/3500, and Dodge 2500/3500 vehicles, exceed this weight limit and are therefore not tested and have no official fuel economy rating. The EPA also does not test motorcycles or four wheel vehicles that are not legal for highway driving like neighborhood vehicles. Beginning with the 2011 model year, passenger vehicles (vans and SUVs but NOT pickup trucks) up to 10,000 lbs will be required to have fuel economy labels.