There have been load of threads and discussion about power sports engine oils. After reading and absorbing much information, I've concluded that there are loads of great oils out there, but I've (at least for now) settled on Mobil 1 4T 10W40 racing oil for my 09 Ranger. It's loaded with phosphorous/ZDDP which is good for flat tappet/valve train wear. It has an excellent addictive package for engine cleanliness, etc. There's lots of info on their website about this oil. I called their customer service rep. and he highly recommended this oil for the Polaris Ranger. The 0W40 oil is designed for modern auto engines with roller rockers and has no where near the valve train protection of the 10W40 racing oils, although it may have enough. It's interesting that the rep. did not recommend it. He did not recommend against it. It just was not mentioned when I asked for advice on best oil for my application. He was really strong on the 4T 10W40 racing oil.