Use the right oil for your car. You can improve your vehicle gas mileage by 1 to 2 percent by using the manufacturer's recommended grade of motor oil. This will help to lower the friction.
Inspect your battery.
Summer heat can be harmful if your battery is over five years old. Traditional lead-acid batteries should be tested and serviced to ensure clean connections between the posts and cables. If battery caps are removable, check fluid levels. Make sure cooling system items are in good working order. Look for cracks, bulging or other signs of deterioration of your radiator, cooling fans and hoses.
Check your tire pressure once a month.
Buy a digital gauge and keep it in your glove box. Compare the pressure in your tires with the recommended pressure listed in your owner's manual and on the placard located in your car door. Then inflate your tires as needed. Be sure to check tire pressure when your tires are cold. A good time is early in the morning after your car's been idle overnight.
Keep your engine in tune.
Fixing a car that is out of tune or has failed an emissions test can boost gas mileage by about 4 percent. So be sure to give your car regular tune-ups. You'll also want to watch out for worn spark plugs. A misfiring spark plug can reduce a car's fuel efficiency by as much as 30 percent. Ensure your mechanic checks for them.
Use your garage for your car.
Clear it out and make room for your car. Parking in your garage will help your car stay warm in winter and cool in summer, and you won't have to depend as much on your gas-guzzling air-conditioning or defroster when you drive.