Motor Oil and Your Engine
When it comes to the overall performance of a vehicle’s engine, motor oil matters. It provides much-needed lubrication and protection against common causes of engine stress, including heat, deposits and wear, and even helps improve your vehicle’s fuel efficiency.
Motor oil is available in a variety of viscosity grades and API performance levels. SAE 5W-20 and 5W-30 are the most common viscosity grades for gasoline engine cars and trucks, and 15W-40 is the typical grade for diesel trucks. The most current performance levels are ILSAC GF-5/API SN for gasoline engines and API CJ-4 for diesel engines.
It’s important to check your owner’s manual to see which viscosity grade and performance level are recommended for your vehicle’s engine. Manufacturers often recommend oils that have been licensed by API as these oils have been rigorously tested to ensure they meet API’s engine oil standards. Manufacturers also typically recommend you use an oil meeting the most recent performance standard. For example, if your owner’s manual recommends an oil that meets the latest ILSAC performance specification, then GF-5 is most likely your oil even if GF-4 is the specification listed in your owner’s manual.