Choosing motor oil can be confusing, with labels like synthetic vs. full synthetic vs. conventional, and at some point you may have wondered if non-detergent oil was ok for your car. For most modern cars, detergent motor oil is the wrong choice because it not only helps prevent carbon build-up, but also lacks the additive package that helps keep contaminants suspended, sludge under control, and engine parts protected. Modern API engine oils are formulated for current gasoline and diesel engines, while non-detergent oils are generally obsolete for normal automotive use. Also, like these additives, detergent motor oil can increase your engine's lifespan and performance. Some vintage-engine sources also note that switching a dirty old motor from non-detergent to detergent oil can loosen deposits that then circulate through the engine.