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. 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.