I've been using Amsoil for a bit over two years now, both 2 stroke and 10-40. Had excellent luck with both. With our relatively short growing season I change oil in the mowers and tractor only once a season. It does not burn and turn all black like conventional oils do. The oil in the 25 Kohler on the Lazer has over 100 hours now and you can still see the marking on the stick through the oil. They claim that their oil runs cooler, I believe them, less dieseling and run on since I switched to Amsoil. For $20 a year you can get a dealership and buy factory direct. I'm also using their synthetic ATF on the tow/plow trucks where the higher temperature capabilities are well worth the cost.