Friday Fuel Economy: Choose the Right Motor Oil

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Next time you change your oil or have it changed by a mechanic, be sure the new lube is the grade recommended by the automaker. Using the right viscosity (a measurement of the oil's thickness) of motor oil can improve your gas mileage by as much as 2 percent.

Even if the recommend motor oil grade is more expensive than other options, you'll save more over time in terms of maintenance and gas mileage with the right grade. Check your owner's manual to know which grade is best for your car.

Ever wonder what those letters and numbers in motor oil grades mean? For single grade oils, such as SAE 30, the SAE stands for Society of Automotive Engineers; the number after refers to the oil's viscosity.

But most current oils are multigrade, such as 5W-30. Multigrades use polymers and are designed such that you don't have to use a thin oil viscosity in the winter and a thicker viscosity in the summer. The W stands for winter, and the number paired with it reflects the viscosity during cold temperatures. The second number refers to the viscosity at higher temperatures. The lower the number, the thinner the oil.


John Rockhold is a green car enthusiast and Contributing Editor for MOTHER EARTH NEWS. Find him on .