We all know that our cars need engine oil in order to operate smoothly. The role of engine oil is to keep the moving parts of the engine lubricated, to protect them against rust corrosion, and -- with modern detergent oil additives -- to keep them free of sludge and general engine gunk.
But most of us also know some things about engine oil that aren't actually true. For instance, isn't it always necessary to change your oil every 4,828 kilometers? And when the color of your oil starts becoming dark, doesn't that mean that it's about to fill your engine with harmful sludge?