Aftermarket engine oil coolers are useful in increasing the lifespan of the engine oil and also in reducing the general operating temperatures of the engines. Although they are not required for towing any Class I and some of the Class II trailers, they are recommended for Class II with higher weight and all the Class III trailers. Some of the parts that constitute the engine oil cooler systems include, an adapter that replaces the oil filter, remote filter mounting, multi-lube, finned heat exchanger located in front of the radiator or air conditioning condenser. As for the trailer towing, an automatic transmission type is also rather popular because of its high reliability and rather simple control. But towing raises the temperature of the automatic transmission fluid, which is not good for the transmission. Hence, it is necessary to install an automatic transmission cooler. This cooler, which is made up of multi-tube finned heat exchanger, is normally mounted ahead of the radiator or the air conditioning compressor, and connected in-line with the inlet line of the transmission cooler tank. Capacity of the cooler must be enough to provide enough air flow for cooling based gross weights of the vehicle and trailer; also additional aftermarket cooling cooler is advised to be installed together with standard radiator cooling tank. When deciding to replace only the radiator cooling tank, a cooler that is twice larger than would be expected should be chosen. Further, a transmission cooler may occasionally result in gear progressing slowly or roughly at low temperatures, and until the liquid warms up to the normal working temperature; some models have a thermally controlled bypass valve that controls fluid circulation depending on its temperature.