Almost one third of the heat generated by the engine must be removed by the vehicle's two cooling systems. Your engine has two cooling systems. 1) The top of the engine: the area around each cylinder in the engine block, the combustion chamber areas in the cylinder head and the intake manifold, dispel heat through the engine's radiator coolant system.(2) The rest of the engine: the crankshaft, bearings, camshaft, lifters, connecting rods and pistons are only cooled by engine oil.
The best working temperature for oil in a car engine is between 82 C - 93 C. The longer your oil can operate within these temperatures, the longer your transmission and engine will last. As oil overheats two things happen. It loses both its lubricating, as well as its cooling properties, leaving your engine at severe risk of damage.
To prevent oil overheating, an oil cooler in the form of smaller, separate radiator is tasked with dissipating the heat within the oil and maintaining the oil supply at a consistent, optimal temperature. Oil coolers for any car and in particular oil coolers are readily available here at Euro Car Parts.