Replace the spark plugs in your engine regularly. This way, the air and fuel mixture will burn cleaner and more efficiently. Improve the intake/output system. By allowing gas to get in and exhaust to get out of your vehicle you will improve the vehicle’s overall performance and gas mileage. Reduce friction. Use high-quality or synthetic motor oil. Check your oil! Low oil makes your engine work harder. Change your filters. Dirty filters can sometimes increase the amount of fuel your vehicle uses by as much as 10 percent. Keep tires properly inflated and aligned. Check regularly to ensure your tires are fully inflated and your alignment is good. Get regular engine tune-ups and car maintenance checks. A lot can go wrong with a car. Damaged spark plugs or transmission problems can also contribute to poor gas mileage.