Why Does My Gas Mileage Vary?

Estimating gas mileage is something that the Environmental Protection Agency leaves in the hands of car manufacturers. The mileage that you see published on the window sticker represents an estimate for city and highway driving as well as a combined mileage estimate based on 55 percent local driving and 45 percent highway driving.

Gas Mileage

Although the EPA estimates offer a good guideline, your mileage will likely vary. And, lest you think manufacturers can submit any number and get away with it, that is not the case. In November 2012, Hyundai and Kia admitted that it had overestimated fuel economy on a number of its vehicles and has been fined by the EPA. Moreover, the two Korean companies will have to compensate affected vehicle owners and will likely face multiple lawsuits over erroneous MPG claims. An EPA audit of the two companies followed extensive consumer complaints about lousy gas mileage.

gas mileageAccording to the EPA, your gas mileage will still vary and for the following reasons:

1. How and where you drive — Clearly, if you put the pedal to the metal and are one to use your vehicle as a race car, then your gas mileage will come in lower than the EPA estimates. Also, if nearly all of your driving is around town, your gas mileage will fall. Then again, if you do extensive highway driving and use your cruise control, you can get better gas mileage.

2. Maintenance and condition — If you follow your manufacturer’s recommended maintenance intervals, keep your tires properly inflated and change your air filters before they get clogged, then your gas mileage will not suffer. Neglect your maintenance and you will see your fuel economy fall accordingly.

3. Types of fuel — Winter blend fuel is less efficient than summer blend and E85 fuel will cause your gas mileage to drop by up to 30 percent. Use the grade of gasoline that is recommended for your car.

4. Vehicle differences — No two vehicles are alike and weight differences of several hundred pounds are possible. For instance, all-wheel-drive generally adds weight to a vehicle. Added equipment including roof rails, door steps, larger wheels, safety features and an extra row of seating can also impact gas mileage. By the way, the fuel economy estimates are for a vehicle with a single occupant; fill up your SUV with seven people, lots of luggage and pull a camper and your gas mileage will plunge.

5. A new car — New cars still have a break-in period ranging from approximately 500 to 1,000 miles. This means that the piston rings on the new engine still have to adjust and your gas mileage will come in lower, at least initially according to CarTalk.com.

(See AlsoFuel Types and Your Car)

Your Mileage

Yes, your fuel mileage will vary and will often come in under EPA estimates. However, you may be able to beat the averages too by babying your car, taking it easy on the accelerator and the brake, and using cruise control on the open road.

See AlsoTop Tips for Getting Better Gas Mileage

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