More or less everyone understands that the principal role of engine oil, or some other lubricant for that matter, would be to present a barrier between moving components, preventing wear and friction.
Moving components that continuously change management like the reciprocating movement of the pistons and connecting rods create a certain amount of shock in the loading move once it changes directions. You can get an emergency fuel delivery service through the internet.
The pistons and rods in a motor that's running a continuous 3000-RPM, state cruising at highway speed are shifting direction 50 times per minute.
The motor oil along with its anti-wear additives must cushion the blow. The oils film is there to absorb and disperse the energy over the load-bearing surface preventing metal-to-metal contact.
Motor oil; even in water-cooled engines also play a roll in keeping the engine cool. The oil absorbs engine heat and transfers it away from hot engine parts.
The oil splashing up into the cylinder not only lubricates the piston's rings moving against the cylinder wall but also carries heat away from the back of the piston moving it to a location that it can be dissipated.
Oil slashing up into the cylinders also acts as a dynamic seal where the piston rings contact the cylinder both lubricating and preventing hot combustion by-products from getting past the rings and contaminating the oil.