Today we're going to take a look at the Flex-A-Lite heavy duty engine oil or transmission oil cooler. This one has the 1/2 inch NPT female fittings on the end here and it's a Class 5 rated cooler. This heavy duty oil cooler can be used for engine oil cooling or transmission oil cooling. Basically, your engine will function at its best when the engine oil is usually between about 180 and 200… see more >