Lucy Lazarony from Bankrate.com (via Yahoo! Finance) has put out a very useful list on how to be more fuel efficient with your existing vehicle:
Fill up with a lower-octane gasoline. Buy the lowest grade or octane of gasoline that is appropriate for your car. Unless your car requires premium gasoline, filling up your car with high-octane fuel is a waste of money.
Don’t top off. Don’t bother topping off when filling your car’s gas tank. Any additional gas is just going to slop around or seep out. Stop pumping at the first indication that your tank is full when the automatic nozzle clicks off.
Tighten up that gas cap. Gas will evaporate from your car’s gas tank if it has an escape.
Go for the shade. The hot summer sun that makes the inside of your car feel like a sauna also zaps fuel from your gas tank. So park your car in the shade of a building or tree whenever possible. And buy a good windshield shade. A windshield shade blocks sunlight and helps to keep heat out of the inside of your car.
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.
Pump up your tires. Don’t get caught driving on underinflated tires. Underinflated tires wear down more quickly and they also lower your car’s gas mileage - by as much as 15%.
Check your tire pressure once a month. 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.
Replace air filters. Replacing a clogged air filter could improve your gas mileage by as much as 10 percent and save you 15 cents a gallon.
Use the right oil. You can improve your car’s gas mileage by 1 percent to 2 percent by using the manufacturer’s recommended grade of motor oil. Opt for motor oil with the words “energy conserving” on the API performance label.
Don’t skimp on maintenance.