Maxima, Bel Ray, Yamalube, Klotz.......
I have always used yamalube, but thinking of trying maxima 10w-40.

 

When it comes to engine protection,oil is the front line of defense,some don't even consider price,just the quality. I have heard a lot of others run auto oil, just change it a lot more,with no problems. I used to run Yamalube,really good stuff,but being the cheap a$$ I am, a couple of years ago, I found a brand called Trophy,it is sold at Mills Fleet Farm, it is 4 stroke wet clutch rated, and is OEM certified by all major bike manufacturers.It only runs 1.65 a quart,and I have ran it for 2 years in hard service,with no problems. In the end it comes to this - what you trust and feel confident in, and how much price means to you. If you keep clean oil in your quad,it is hard to go wrong. The only exeption to the rule is any auto oil rated "energy conserving",this has friction additives that will cause slipping in wet clutches.