I posted this on a CR500 forum I visit: Here's a question sure to spark debate. I've always run synthetic Red Line at 40:1. My dad has been working on air-cooled 2-strokes since before I was born. I was tearing down my '97 500 and he asked me what ratio I ran my oil at. We started talking about ratios for different stuff and I brought up the Amsoil 100:1 stuff out now. I mentioned that I would be pretty skeered about running something like that. He mentioned that he has sold an Oregon 100:1 mix for quite awhile for chainsaws and has never had a problem with them. He contrasted a liquid-cooled modern mx motor in fairly optimum conditions temp-wise that isn't wfo all day versus an air-cooled saw that has the throttle mashed down, the motor loading up big time, and the fins packed all full of sawdust and dirt. I figured he had a point and the Red Line Oil I use states it can be mixed up to 100:1, but that's a step I'm not willing to take. I was wondering what's the highest ratio in here people have heard of going to for bikes?