And I'll tell you something else people do not understand. One of our company's was the distributor for Wisconsin engines. "Large 40-100hp air cooled engines". When a air cooled motor is running the oil and the air cool the motor, plus heat is emitted through the cooling fins. Now when you get stuck in traffic, you loose 1 of the three characters , air. Now here is where people really mess up. They get stuck in crawling traffic and keep starting & killing there bike. Now you have lost two of the three cooling characters, oil and air and you are solely dependent on the fins to displace the heat, which for 5-15 minute will actually raise when a motor is turned off! Wisconsin motors did not have oil coolers, they actually used huge oil pans. So to say oil coolers help, yes they offer 3 factors. (1) extra oil in the system. (2) more cooling fins to disperse heat. (3) air cooled radiator to cool oil down before being returned to the oil tank. And that's all a oil cooler actuall is is a air cooled radiator to disperse heat. In normal operations a S&S motor can dispence the heat the motor generates. When above conditions are a factor 1 oil cooler will help, in extreme conditions 2 is needed. Now for the down side. Engines get hot and cool down. When this happens they actually make condensation inside the motor. So you get water in your oil. Not much but slightly. When your motor heats up to 180*-200* the heat of the oil & motor burn off this fluid. When you have 2 oil coolers and ride in the winter or cooler months you only build heat up to 140*-160* you trap this moisture and it breaks down your oil. That is why I have diverter valves on both bikes. I only open my diverter valve when I know it is either hot riding or I will be in heavy traffic that day. Jagg makes a small manual diverter valve I run.
with out a oil cooler my HD was 220* range, so it cooled my oil 40*. Also I removed my ambient Temp gauge from my dash and plumbed in a oil temp gauge. The thermometer tail is Tee'd in the oil line just when the oil leaves the motor. So I have exact engine oil temp.
