I didn't even know they made 5wt-50 oil. I kinda forgot to do the break-in oil change on my Polaris, so just yesterday got the manual out, and they call for 5wt-50 oil. In a few calls, couldn't find it locally except an the Polaris shop, where they sell TWO quarts for THIRTY bucks. What?!? I ended up ordering a 6qt case of Mobil 1 off Amazon for $45. Mine, and I guess most Polaris models take ~2 quarts.
I'm trying to figure out why Polaris calls for this oil, as from perusing forums, they seem to be the only ATV/UTV manufacturer that does. My Honda Rancher uses 10wt-40, or depending on climate, just like with cars you can use 5wt-30 or a couple of other ranges. The Polaris manual list 5wt-50 only, and doesn't even have a shared oil pan/transmission like my Honda does (which is a valid reason to use ATV formulated oil, a gallon of which is $25).
On a couple of the Polaris forums, a theory was that the engine design Polaris uses beats down viscosity, which is why the want the 50wt. Some guys were using synthetic 0wt-40, or just diesel oil like 5wt-40 Rotella. I only went to the 5wt-50 Mobil 1 because of the engine design theory (though I have no idea if that's true) and not wanting to take any chances until I can study further.
Still, it seems like an odd oil choice. One plausible theory I saw was that it's partially marketing. Since 5wt-50 is apparently hard to find in many locales, people will give up, go to the Polaris dealer, and pay $15/qt for their crappy oil.
