Despite lower gas prices, it's always a good idea to maximize the fuel efficiency of your car whenever possible. One easy tip to improve your average miles per gallon is to take a look at your car's owner's manual. Find out what grade of motor oil is recommended; by using the recommended grade, you can improve your efficiency by 1 to 2 percent. Sometimes the recommended grade is actually the cheaper one! And always have your oil changed at a professional service station; all used motor oil is collected and recycled at a refinery.