You will never have to worry about wearing an engine out unless it is modified and raced. I have seen engines fail too soon when its owner makes poor technical decisions, which is often. Corrosion and lack of maintenance, by far, end up killing engines long before they would have failed otherwise. The best oil for corrosion protection is also the cheapest, TCW-3. Its temp range will never be exceeded if you dont make power for very long, perfect for free riding. Always dry run the engine until the temp sensor shuts it down and store the ski with the hood propped open. Your skis second owner will thank you.