I am sure this is probably covered, and I tried searching for it, and reading the stickied post at the top but didn't really find an answer. Can I just go to walmart and buy 10w-30 oil for my Kholer Courage 22hp mower on my Cub Cadet? Does it have to be lawmower oil or is oil for an automobile fine too? Any oil better than the rest? Synthetic? Thanks!