Top 10 Misconceptions about Fuel Economy


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WASHINGTON - May 12, 2010: Fueleconomy.gov, the official source for EPA fuel economy ratings for automobiles, has compiled a list of the Top 10 Misconceptions about Fuel Economy (http://www.fueleconomy.gov/feg/topten.jsp). The list was developed in response to questions frequently asked by the site's users and based on input from fueleconomy.gov's staff of automotive engineers and a panel of experts from auto manufacturers.

Even auto enthusiasts and knowledgeable consumers may find some surprises on the list, because several of the misconceptions generally held true and were considered common knowledge in the not-so-distant past. However, rapid changes in vehicle technologies have made several of these "truths" obsolete or less pervasive.

For example, changing a dirty or clogged air filter could improve your fuel economy significantly in the past, when most vehicles had carbureted engines. However, modern computer-controlled, fuel-injected engines regulate the air-fuel mixture so well that a dirty air filter does not decrease fuel economy-although it can still affect performance. Also, it was once typical for a vehicle with a manual transmission to get better fuel economy than the same model equipped with an automatic due to the added weight and energy losses associated with the automatic transmission. However, newer automatic transmissions are lighter and more efficient, and it is not uncommon for an automatic-equipped vehicle to achieve fuel economy as good as or better than its manual-equipped counterpart.

Fueleconomy.gov provides an explanation for each of the following Top 10 Misconceptions about Fuel Economy:

1. You have to drive a small car to get good fuel economy.

Advanced technologies like hybrid drivetrains, diesel engines, 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 2010 model year, five of the top ten most efficient vehicles are midsized cars, with a midsized car taking the top spot.

2. Manual transmissions always get better fuel economy than automatics.

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 at http://www.fueleconomy.gov/feg/findacar.htm.

3. It takes more fuel to start a vehicle than it does to let it idle.

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. Restarting your engine too frequently can wear out your starter.

4. Vehicles need to warm up before they can be driven.

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. As a vehicle ages, its fuel economy decreases significantly.

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. Replacing your air filter will help your car run more efficiently.

This is true for older vehicles with carbureted engines, but modern fuel-injected engines have onboard 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. Aftermarket additives and devices can dramatically improve your fuel economy.

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. Using premium fuel improves fuel economy.

Unless your vehicle was specifically designed for premium fuel or knocks severly with regular fuel, you will probably experience 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).

9. The EPA fuel economy estimates are a government guarantee on what fuel economy each vehicle will deliver.

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. All vehicles are tested for fuel economy.

Current testing regulations only require light-duty vehicles of 8,500 lbs or less to be tested for fuel economy. 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.

Fueleconomy.gov will soon release other Top 10 lists, including the most fuel-efficient vehicles of the past 25 years and the most efficient vehicles as reported by actual drivers.


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