What is the advantage if having an Oil cooler? Is it just an extended gas tank? Please give input.

 

It works kind of similar to a radiator. The oil is pumped from the engine to the cooler where air can pass over the cooler and the heat can disapate into the air. Your engine runs cooler and if you have an Air cooled four stroke that is highly modified they are a must. Unless you like overheating engines and oil turning into sledge after a few hours of riding.