Basically, automatic transitions are equipped with an oil cooler which is located inside the radiator. An aftermarket oil cooler like Replacement AT oil cooler, when installed in the radiator provides improved cooling and is preferable for towing or high performance applications. Most engine, except for those air-cooled do not use an oil cooler. Normally, an engine’s cooling system is sufficient in maintaining the oil temperature within the safe levels.
Now, a wise move to make when installing an external oil cooler is to install it in conjunction with a full-flow oil filtration system. In this case, it is installed downstream of the filter that is usually found on the other side of a thermostatically controlled valve. The external oil cooler and filter, depending on the plumbing runs will improve your oil capacity by about 1.3 quarts.
Besides the fact that it can double the life of your engine, the most impressive change you will get to notice is a slightly longer warm-up time. You can definitely extend the oil change period to 3,000 miles under non-dusty condition when a filter is installed. Note that the engine oil does not only serve as a lubricant for moving parts, but more so as a coolant for the crankshaft, rods and pistons. The bottom end of the engine relies merely on engine oil for cooling. For this reason, maintaining the correct oil temperature is critical to the engine's performance and longevity. Since the latest generation of engines are apparently smaller nowadays and run at higher RPMs as well as capable of producing more heat, to keep the correct temperature is very imperative.