Keep your car clean. Mud on the undercarriage can weigh a significant amount and slow you down.

Consolidate your daily trips and errands. This will also save you the cost of restarting your engine, which uses a lot of gas.

Avoid air conditioning when possible. However, when driving at higher speeds, having your windows open also creates drag.

Don’t throttle the gas or brake pedal! Sudden starts or stops use more gas than gradual changes in speed.

Don’t idle for too long. Turn off the engine if you anticipate a lengthy wait.

Limit car warm-ups in winter.

Clear out the trunk. More weight equals more drag.

Avoid high speeds. We know this is almost impossible to resist but you can improve your gas mileage by up to 15 percent driving at 55 mph rather than 65 mph.

Use overdrive. If your car is equipped with overdrive gearing use it as soon as your speed is high enough.

Use cruise control. Maintaining a constant speed is ideal for improving your gas mileage.

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 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 wheels 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.