Some Things You Probably Didn’t Know About Gas Mileage (and How to Improve It)

Illustration depicting a sign with a fuel effiency concept.

The Energy Information Administration estimates gas will cost an average of $3.37 a gallon in 2014. But does that mean you have to buy the one vehicle on the lot that gets the best gas mileage? Several factors influence gas mileage and cause your car to lose mpgs. Before you buy based on a sticker number, understand how real mileage ratings work and how to get more mpgs right now.

Driving Habits

Your driving does impact how much gas your car uses. Aggressive driving could cause you use up to 33 percent more, according to U.S. Department of Energy (DOE). Speed is perhaps the biggest variable in gas mileage—for every five miles over 60 miles per hour you drive, it costs an additional 24 cents in gas a mile, the DOE reports. Accelerating suddenly uses more gasoline, since your engine works harder to produce more power in a shorter period of time. If you start and stop fast all the time, you’ll drain your tank faster. Reduce your speed to 60 miles per hour and limit sudden acceleration and stopping to a minimum, and you’ll increase gas mileage.

EPA Estimates Aren’t the Actual Mileage

The Environmental Protection Agency (EPA) estimates mileage based on tests using a dynamometer, and tests recently updated for 2008 vehicles. However, those tests are performed in a laboratory and don’t include factors like head winds, inclines, towing weight and rough terrain, or even atmospheric conditions.

The amount of oxygen your engine receives also impacts mileage. In more humid areas, your car intakes less oxygen and therefore produces fewer mpgs. Colder engines are also less efficient. Until your car warms up, it won’t produce the mpg it is rated for.

Size and Weight Matters

Not all small cars are more efficient. A car with a small engine running up hilly terrain could use more gas because it lacks a powerful engine. Torque (the power exerted to turn your wheels at startup) helps your car or truck ramp up to a higher speed faster, especially while pulling a heavy load. That load will cut into your mileage. A small engine will expend more gas to pull that load if it has lower torque.

However, driving a big truck (especially on short trips) guzzles much more gas. Big trucks use more gas at idle and to accelerate. For instance, when driving a 2013 Ford 150 around Phoenix, you only get 15 mpg in the city (and 21 highway). A smaller car like the Hyundai Accent GLS gets 28 mpg in the city, almost twice as much.

Driving 200 city miles a week in the Ford, you’ll spend $2,336.53 a year on gas. Meanwhile, you’ll only spend $1,251.17 in the Accent. That’s a savings of $1,084.81 a year. There’s always additional discounts available on the GLS from certain dealers in your area. Just be sure to check online and research prices, options and mpg ratings first. Take time to compare prices and features on new or used cars on Kelley Blue Book or another reputable site for even greater savings.

Keep It Clean

Keeping your engine clean also influences gas mileage. Clogged intakes or injectors reduce gas mileage. So, your older vehicle’s actual mileage rate can vary wildly depending on how well it has been maintained. Cleaning injectors and regular oil changes will maintain better mileage rates.

Tom Moody, the author of this post, is a retired auto mechanic who blogs about cars from his California home.

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