Do you need to pay extra for CAT Oil or Quicksilver etc. when you can buy seemingly good oil at a big-box store for half the price? More to the point, will using one of those alternatives jeopardize your engine or, worse, void your warranty?
To answer that, you need to start with the API rating. The American Petroleum Institute establishes minimum performance standards for all motor oils, which are accepted by engine manufacturers. These ratings consist of an initial letter indicating whether the oil is approved for gasoline (S) or diesel (C) engines, followed by another letter, and sometimes a number, indicating the generation of the oil’s additive package. For instance, the most advanced additive package available is in oils designated SN for four-cycle gasoline engines and CJ-4 for diesels. As the second letter progresses from A, the oil’s formulation is newer and more advanced. Some oils are approved for gasoline and diesel engines so they carry both designations.