An oil cooler is essentially any device or machine intended to cool oil, but in most instances people talk about it in the context of cars, trucks, and sometimes airplanes. In these settings the cooler basically acts as a small radiator that helps keep an engine cool by keeping the oil supply at a consistent temperature. Cooled oil helps keep the engine running smoothly, particularly during gear changes in very hot weather or on long-haul trips when things might otherwise have a tendency to overheat and break down. Not all cars and trucks use oil as a coolant, but those that do really depend on a working cooler in order to get good efficiency and performance.
Automotive engines tend to be somewhat complex, and usually depend on a series of different combustions, heat sources, and temperature regulators in order to function properly. Oil coolers are most common in heavy-duty machinery that has a more industrial-grade engine. Trucks used to haul freight and large vehicles designed for off-roading are two common examples; some recreational vehicles (RVs) and airplanes have them, too, and they may even be found in certain motorcycle models. Race car drivers sometimes add them to sports cars to make them more efficient, too, and to improve their fuel combustion times.
A transmission oil cooler is often considered essential in high-strain situations because a transmission's lubricating fluid heats up with each gear change. While not crucial for highway driving when vehicles more or less stay within a few gears, transmission 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.
Even though the main job is to cool and lubricate the engine, this part can also act as an important coolant for a number of other parts. A motor's bottom end, which includes parts such as the crankshaft, bearings, camshaft, rods, and pistons, is also cooled only by engine oil, for instance, and this cooling can impact overall performance just as much as it could in the engine itself.
Engine oil cooler design can generally be split into two types. Tube and fin models are the first, and are designed so that oil circulates through cooler lines that surround the engine. As the oil moves away from the heat of the central engine, its temperature drops and excess heat is funneled out by fin-like vents attached to the tops or sides. Stacked-plate designs, by contrast, force oil through a series of metal plates. Heat dissipates as air moves across the plates, and the oil cools faster when it has greater surface area and is shallower, too.
Plated models are often slightly less effective at cooling oil than their tube and fin counterparts since they’re more passive, basically waiting for cooling to happen on its own. A lot of this depends on the application, though. In some settings, stacked plate coolers make more sense.
How They Work
In a stock setup, transmission fluid is cooled as its collected heat transfers to the colder engine coolant that surrounds it. Coolers usually work best when mounted in front of a stock radiator since this is where it can often get the most unobstructed source of cool air. This, in turn, allows much cooler fluid to return back to the transmission case.
While a majority of cars are not manufactured with proprietary engine oil coolers, there is a large aftermarket for them in many places, and they are common accessories in vehicles involved in towing and other heavy-duty applications. People can buy oil cooling kits to upgrade their vehicles themselves, though this usually requires a bit of expertise. Many professional shops will also install these for people looking for ways to make their machines more efficient.
The optimum temperature for oil is usually between 180° and 200°F (82° and 93°C). Failures start to occur when oil cannot dissipate its collected heat fast enough and rises past this threshold, which can begin to degrade the oil. Oil loses its lubricating, as well as its cooling, properties when it starts to break down, and this can lead to a number of serious engine and transmission problems. Coolers should usually be inspected fairly regularly to keep them in good working order, and owners should take care to regularly inspect and service them to avoid major failures.