...why pay the same price for less temperature protection?
I agree with that--but I have a different perspective on it. There are good group III oils on the market that do a fantastic job of mitigating wear metals and corrosion--even in very hot engines.
I think that the generally elevated metal counts in group IV and V synthetic UOAs that we see (and
please don't treat this as personal opinion, it's a
FACT--read the UOAs here) are more owing to corrosion than to the PAO's ability to lubricate.
While it is true that the group IV and V oils will fare better in extremely hot environments, this is overkill. Take a look at this UOA which I did a couple years back:
http://theoildrop.server101.com/forums/s...true#Post714572
You will see that the group III Havoline PCMO oil did
extremely well. The engine of my bike got so hot during that OCI that it actually didn't want to stop running when I switched it off one day. (Had to put it in gear and kill it by dumping the clutch). And there were other 100 degree riding days during that OCI.
So the point is, if the group III Havoline oil can perform this well, and turn in a UOA which beats
virtually every other synthetic oil Harley UOA on the board, we have reason to believe that a group III oil can endure some extremely hot conditions and still work very well.
Now. The other side of the coin is this: What about the corrosion/rust inhibiting qualities of the oil you're putting in your engine? Are you willing to accept an excess amount of rusting in trade for 50 or 100 degrees of high temperature protection that you won't ever need?
Realize that by the time your engine has gotten hot enough to need a group IV oil to save it, it's TOAST ANYWAY!!
None of us know how much group III (if any) is in this Amsoil motorcycle oil. I think a STRONG case can be made for a significant group III content, based on reasons I've already stated. I'm not knocking Amsoil here--I'm actually commending them for producing a product which has turned in a better motorcycle UOA of any previous Amsoil product. I just think that they've probably used a fair amount of petroleum oil to do it.
Dan