Originally Posted by moth898

I'm running my shark stock, no shims added. There is no reason to run 30% for off road, all it does is make the engine run hot and hard to tune. I'm running 20% O'donnels speed blend with a extra ounce of caster oil added. I got the advice on nitro content and the oil from one of the top tuners in California. My engine had a smooth idle, no flame outs and nice throttle responce. Use any 20% with a little extra oil for security, you don't want to be popping that pricey engine. 30% nitro is a engine killer, only go to 25% when you have trouble holding idle or flaming out. He told me to use 25 if i get to my third or fourth gallon through a motor.