why cant we use regular engine oil in our engines compared to the high dollar stuff? we run regular oil such as castrol 10-40,5-30,20-50 in the car so why not in the bikes? what makes them so different? the heat? they both have combustion,heat, pistons, valves cranks and cams etc. Why pay the high price for special oils for a bike when you can run "regular oils in a car engine and get 300,000 miles out of them? even if ou had to change the oil more often due do excessive heat for the price of regular castrol 20-50 a person could change the oil 3-4 times compared to once for the same price of special motorcycle oil. Go easy i just came from the metric side so im still getting used to having 3 different oils for 3 different places. on metric everyting shares one oil. I ran rotella t6 in it and it had over 106,00 miles on it. Anyone run rotella t6 in their bikes? if not, why? it is a full synthetic oil. i read several post but people only mention the rotella never really say yes or no about using it. Since its just the engine why should it be the non energy conserving type? if it shared with the clutch or other things like a metric i could understand but the engine stands alone like a car.