Considering the amount of air that an Onan moves at full throttle, there is ZERO need for any type of fan between it and the grill...period. The problem arises when folks are not keeping things clean, not adjusting valves or have a lean carb or most importantly, not running the engine at full 3600 rpm while doing ANY kind of work. I cannot stress that enough as a 30+ year small engine technician with factory master tech certification for all of the major engine brands including Onan. Folks seem to think that running at a lower rpm creates less heat, but the opposite happens, there is not enough air movement by the flywheel to cool the heat that is being made, so the engine gets much hotter than it would if the operator was running the engine at full power. Checking the RPM's(no load and under load) is something that is part of every full service I performed. If its off, either to high or to low, it gets adjusted so I see 3600 with the PTO engaged. And usually no more than 50 to 100rpm higher with the PTO off. A bit of overspeed with no load is required so that it falls back to 3600 under a load or darn close to it. While I have a laser reading temp gun, I plan to put a gauge that gives me cylinder head temps on both cylinders of my 420's Onan P220. This way I can see how things are going while mowing or at a plow day. With the cost of doing any major engine work going up and up, better safe than sorry. I have a small crack in the hood at dash end from an overly tight hood latch(PO did this not me), so I am going to put a small twin gauge pod there with oil pressure and cylinder head temps, That will hide and reinforce the crack area so it does not spread any more, and give me some needed engine info. The paint is to nice to have the whole hood redone at a body shop to fix the crack right now.