Q: What is Miles Per Gallon?

December 17, 2013 12:53 PM

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You'll see the term "miles per gallon" or "mpg" constantly when researching the purchase of a new or used car. This measurement is commonly associated with fuel economy. A vehicle's fuel economy indicates how efficiently it uses fuel. In America, this is expressed as the number of miles per gallon (mpg) of gasoline.

The miles per gallon rating is important for many reasons. Higher mpg ratings save you money at the pump, and the federal government carefully monitors fuel ratings and their impact on the environment and economy. The Environmental Protection Agency (EPA) tests vehicles for fuel economy in the United States and sets requirements and guidelines for automobiles operating in throughout the nation.

EPA regulation labels are affixed to vehicles or car specification sheets found at dealerships. Whether you're buying a family car, truck, or a motorcycle, you should see a page or sticker with a breakdown of the vehicle's fuel economy. This includes both highway and city mileage, along with the estimated cost of annual fueling. The information might also list "combined" mileage, which is a weighted average of the highway and city mpg figures. This provides a quick review of the car's overall fuel economy.

The highway and city mileage ratings result from testing by the EPA on vehicles that are the same make, model and manufacture year as the vehicle you're reviewing. Highway mileage is measured by EPA officials who test a warmed-up engine at speeds of 48 to 60 miles per hour (mph) over a stretch of 10 miles with no stops. This simulates the experience the driver would have traveling along a state highway or interstate. City testing involves the use of a cold engine and includes 23 stops over 31 minutes. Speeds average about 20 mph and top out at 56 mph.

Along with this basic testing, the EPA also conducts controlled tests and field tests. The organization may run three different supplemental tests on vehicles to confirm results and to test for emissions and similar factors. Each test carefully measures the amount of fuel consumed, while some also measure waste product output.

Minimum guidelines for fuel economy in the United States constantly change, usually trending upwards, which makes high miles per gallon, that is, exceptional fuel economy all the more important to carmakers and all the better for you. The efficiency of your new vehicle at burning fuel can have a lasting impact on your wallet.

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