My thought is with a carbureted sled, any quality two-stroke oil formulated for snowmobiles will work ok. I don't know of anything wrong with running the best synthetic oil out there, but there's less to gain. The newest formulas are super thin to help them circulate in the "dry" crankcases on EFI sleds; it might be thinner than you'd want without the gas to slosh it around though. Oils like VES were developed to minimize deposits on exhaust valves: most if not all benefit is not having to clean the valves as often. Even with such an oil, you should clean the valves regularly (at least once per season - more often if you ride a lot). But how quickly it builds up depends on the oil, the gas, how you ride it - lots of things. So if they come out relatively clean, you can extend the cleaning interval. Another thing that really helps, you might want to buy a can of something called carburetor dip (could be other names; it comes in a paint can and does wonders to dissolve carbon deposits) to soak the valves in. You'll also want to inspect the diaphragm and springs while it's apart and replace them if they go bad. Anyway, going back to the oil, VES or Interceptor oil are both good if you're mainly looking to minimize maintenance. I used to always run VES in my old sled, but switched to Castrol because it's half the price, Oreilly's carries it, and everything I've read indicates that it'll do as good a job or better, provided I kept on top of the valves.