How does motor oil work?
Reduced friction
Without oil, the internal surfaces would heat up, melt and very quickly seize the engine due to friction. Oil and its special additives form a molecular barrier between moving parts that reduces friction, thereby preventing wear and reducing the heat generated.
Cooling hot spots
Oil cools the parts that the cooling system fluid (based on aqueous solution) cannot wash. Oil gets into the combustion chamber and onto the pistons, the temperature of which can exceed 1000°C. Oil allows heat to be transferred to the cooling system. Oil heat also passes through the air flow blown into the oil pan and through an additional oil heat exchanger.
Cleaning the internal surfaces of the engine
Oil washes away combustion products (mainly carbon) from pistons and cylinders, carrying them to the oil filter and holding the smallest particles in suspension until they are washed away during an oil change.
Type of motor oil
Mineral oils are traditional oils, mainly used in older engines and vehicles not used in severe conditions.
(Article obtained from this portal MercedesMan)
Diesel oils are specially formulated for diesel engines, including turbocharged models and 4x4s. Synthetic oils are the most advanced oils, providing the ultimate protection, but at a relatively high price.
Semi-synthetic oils provide a high degree of engine protection, but at a lower cost than purely synthetic oils.