With today's quality SYNTHETIC OILS, I am not so sure a cooler is needed. These are not RACE BIKES . They are also not thrashed hard off road, not the design of bike. My opinion is that considering these burro's are used off road some, the oil cooler/ cooler lines are looking for a ROCK or TREE to damage them and cause an oil loss. Again.....MY OPINION....just go with appropriate grade of synthetic oil and keep oil clean and fresh.