Ditto on what ^he said. Alot of self taught "oil gurus" on here will tell you to run everything but chaincase oil. For what it's worth, just pick up a bottle of any snowmobile approved chaincase oil and change it. Your 97 should have a drain plug at the bottom so no cover removal required. It's not a bad idea though to take the cover off and inspect the chain, gears and the chain tension if you've never done it before or the sled has higher mileage. This will allow you to clean out the minor filings and grit that normally accumulate at the bottom of the case. It will also give you piece of mind when you are done. If you do want to pop the cover off be sure to have a new seal on hand because they usually leak after 1-2 uses.TRIPLEB said:People will tell you to use everything from tranny fluid to motor oil. I would just use what is supposed to be in there- OEM chaincase oil. You don't use very much and its not that expensive. As far as changing the oil, if you're lucky there's a drain plug in the bottom of the case. If not you'll have to do it the messy way by taking off the cover.