What Is an Oil Cooler?
An oil cooler is a separate, smaller radiator from an engine's main radiator, which maintains an oil supply at a consistent, optimal temperature. Broadly put, lower oil temperatures prolong the life of an engine or transmission. An oil cooler can play an important role in the smooth running of a vehicle by dissipating heat while transporting oil away from moving parts into the oil pan.
The optimum temperature for oil is between 180 and 200 degrees Fahrenheit (82-93 C). Failures start to occur when oil cannot dissipate its collected heat fast enough and rises past this threshold. As it begins to break down, oil loses its lubricating, as well as its cooling, properties.
While a majority of cars are not manufactured with proprietary engine oil coolers, there is a large aftermarket for them, and they are common accessories in vehicles involved in towing and other heavy-duty applications. Oil cooling kits exist for both motors and automatic transmissions. In engines, oil not only functions as a lubricant but also as the coolant for a number of parts. A motor's bottom end, which includes parts such as the crankshaft, bearings, camshaft, rods, and pistons, is cooled only by engine oil.
Engine oil cooler design can be split into two types — tube and fin style, and stacked-plate design. Tube and fin style oil coolers are designed so that oil circulates through cooler lines — the tubes. As the oil circulates, the lines dissipate the heat through the fins. The stacked-plate design forces oil through a series of plates, with heat extracted as air moves across the plates. This more passive design is significantly less effective at cooling oil than tube and fin.
A transmission oil cooler can be essential for automatic transmissions used in high-strain applications, because a transmission's lubricating fluid heats up with each gear change. While not crucial for highway driving, in which gear changes are minimized, transmission oil coolers can markedly improve the performance and longevity of transmissions that are subjected to a great deal of stress. Overheated transmission oil can lead to slower gear shifts, worn seals, lower mileage, and, ultimately, premature failure.
In a stock setup, transmission fluid is cooled as its collected heat transfers to the colder engine coolant that surrounds it. For maximum effectiveness, an oil cooler works best when mounted in front of a stock radiator, as it is there subject to an unobstructed source of cool air. This, in turn, allows much cooler fluid to return back to the transmission case.
Written by Mike Howells
