Consider for a moment what’s required of your motor oil. It has to provide a film of lubrication between metal parts, so that they can freely move against each other without friction, overheating or damage. It has to trap the carbon byproducts of combustion and suspend them so they can be trapped by the paper element in your oil filter. It has to neutralize the acids that are produced during the combustion process. It also has to reduce heat in parts of the engine that aren’t surrounded by a water jacket for cooling. It can’t get too thick in the winter, which would make it hard to circulate on a cold day, but it can’t thin out too much in the summer either. That’s a lot to ask of one substance!
Older motor oils didn’t include additives like detergents and other modifiers that ...[more]