I use the Ski Doo Synthetic Oil becuase of the exaust valves. I was told synthetic keeps them clean. Works like a charm - no engine troubles. However, it smells real bad. I am concerned about changing oil because the new Doos burn so little. There's a whole discussion on it. Can't remember if its on snowmobileworld.com or snowmobilenews.com. Anyway, hate to switch when I'm having good luck, but supposedly the Maxima TundraR is a very high quality oil that does not stink. Of course, I believe everything I read, so there you go!
I want to ride every day, all day, as fast as I can.