I know I am renewing an old thread but I didn't want to start another oil thread. The reason why i started looking is I have a MY 21 850 coming in the fall and I have been running Maxima Tundra oil in my sleds the last 4 seasons, and I buy it by the case so it works out to less than 30 bucks a gallon delivered to your door. The part of the specs where Ski Doo "Has" you so to speak is the SAE grade 4 requirement. I emailed Maxima and the tech told me it does not have a grade 4 rating. this has had me researchin this topic a lot over the past two weeks and as far as I can tell there aren't many oils that meet this requirement. I know for sure that four oils do because they state that they do on their technical data sheets. Amsoil Interceptor, Amsoil Dominator, Motul Snowpower full synthetic, and believe it or not Quicksilver full synthetic snowmobile oil. I have emailed tech support from other manufactures and either haven't gotten a response yet, or got answered with a direct no. the Mystic tech support person I emailed responded with they didn't even know what SAE grade 4 was, and that I should stick to the manufacturers oil for warranty purposes. Also Mystic JT4 full synthetic is not JASO FD rated its only FC rated. The oil company I am waiting for to respond is Spectro, looking at the data sheet for SYN SNO it should meet grade 4 but that's only speculation. Lastly three of the 4 oils mentioned are equivalent in price to XPS ETEC, the cheapest however is Quicksilver at roughly 30 bucks a gallon. If you feel comfortable running Quicksilver, great, other than that is there really a benefit to not running XPS? I don't like spending 50 dollars a gallon like everyone else but I am having a hard time convincing myself that there is.