wade: Welcome to12 proven ways to improve your gas mileage Keep your engine tuned up. Incorrect fuel ratio, bad spark plugs and incorrect spark timing can have a big effect on gas mileage. Don't use your air conditioner (A/C) unless you really need it. The A/C compressor puts an extra strain on the engine. Make sure your tires are properly inflated. Under inflated tires cause more resistance to travel. Avoid stop and go traffic by taking alternative routes or less congested travel times. Ask other pe