I have taken in account water/air cooled, transmission, etc. Most ATV or motorcycle lubes claim they work great for combined systems. The extent of my experience is some training (Noria of course) and some personal research so I don't really have a lot of experience to draw from. With what I have read I wouldn't have expected an Ester to be recommended for this application. I know PAO's have Ester co-base for the additive package but I would have assumed a PAO was best (in this application). Reason being the issues Esters have with water. I imagine the environment of an ATV invites moisture and with the temperature differential condensation would be high also. Why do you recommend an Ester? I appreciate the help and please don't take my questioning as 'arguing'; I just want to learn more and why.