I have an 09 Rancher with ES and am going to switch to synthetic. Is Amsoil 10w40 motorcycle oil a good choice? It say's it is "Not recommended where an API GL-4 or GL-5 gear oil is required". Is a GL-4 recommended for the rancher? Thanks

 

Well I ordered the 10w30 Amsoil since the manual calls for 10w30.

 

10w40 is perfect, 10w30 works well in liquid cooled engines.

 

Would 10w40 have been better?

 

10-40 would offer a little bit more protection in hot temps.

I know you have already ordered the Amsoil but in the future, Shell Rotella 5w-40 synthetic works just as well and is a lot more economical to use.

I started out with Amsoil synthetic in my atvs but switched all of them over to the Shell oil. My Rubicon started out with Valvoline atv oil but I switched it to Shell and I can say truthfully, that all our atvs run just fine on the Shell oil.

Plus, Shell Rotella is now rated JASO/MA for motorcycle use.

But you use what you want.