I run Kawasaki-powered commercial lawn mowers. Their duty is severe and I'd like to try Amsoil. Amsoil has their 4-stroke small engine oil that is described as a robust SAE 30 and 10w30. However, Kawasaki has recently started calling for 40 or 50 weights in their engines. I am wondering if the Amsoil UTV 10w40 would be a better option, but I would like to know the difference in their formulations....and if this is a good idea. ( The engines in question are not under warranty.) please, no discussions on other oil brands. I know plenty of other brands that are also suitable, and understand that.