In the past, fitting an oil cooler was mandatory once an engine had been even slightly uprated. The main cause for this was the quality of motor oils available at that time. If the oil temperatures exceeded a specific point engine failure was almost guaranteed. Modern motor oils are generally of a much higher quality, especially the 'brand names', and have far superior high temperature tolerance than those of 10 or 15 years ago. Fully synthetic oils have extremely high heat tolerance. Use of any of these oils makes an oil cooler less of a necessity where engine outputs don't exceed about 90 horsepower. It is as bad to run the oil temperature too cool as it is to let it get too hot. The ideal operating range is 200 to 230 degrees F (sump temp). At these temperatures the oil is working efficiently to produce the best power, economy and release of combustion by-products. If the oil is too cool, these by-products are absorbed into the oil, requiring more frequent changes to avoid bearing and bore damage. It is worth noting that keeping the oil at the correct temperature helps cool the engine; high oil temperatures will create higher water temperatures.
Various sizes of oil coolers and fitting kits, including pipes, are available. To help control temperature there is a thermostat MOCOT1 that fits into the engine cooler pipes (can not be used with braided steel pipes) that operates at 74degrees C (165degrees F). An oil temperature gauge adapter MOCOT2 is also available that fits into one of the cooler pipes, not compatible with the braided steel pipes.