Gas Mileage - Basic maintenance can save you hundreds of dollars a year in lost fuel or lowered gas mileage. To save on gas, look at your gas cap, inspect it for cracks or damage. Make sure it is installed tightly (with 3 audible "clicks") after each visit to the pump so that your gas does not vaporize away. Check your tire inflation. Poorly inflated tires cause you to lose a mile or two per gallon of gas. Change your spark plugs regularly to prevent misfiring and dirty plugs waste gas. Change your dirty air filters. Dirt, dust, and bugs can cause the filter to release less air into the fuel. This causes a rich mixture which causes fuel waste. Most of all, simply slow down and go easy on jack rabbit starting and stopping.. Driving the speed limit is generally recommended for best fuel economy.