I know M series like 87 Octane, but??

[WyoBoy1000]

I might be wrong but I think on my 07 m1000 its says to run 87 oct right on the sticker that was on the right side on the running board. Says the emissions of the sled meet regulations with 87 oct or something like that. havent looked yet but the 09 sticker is under the seat. Lower elevation creates more hp increasing heat and rate of compression thus the need for higher octane at lower altitude.

 

[Killerk]

The manual on cat sleds state to run 87 octane.
at sea level this is the minimum octane you should run with a stock sled.
As others have stated, as you go up in altitude you can run less octane.
The more octane the slower the fuel/air mixture burns.
People can run whatever they want in their sleds, but on a stock machine running higher octane, especially at high altitude is wasting money and you will loose performance as stated.
Some engines are more finiky... On my 1000 I have run premium when my pa filled my sled (he runs 91 octane with 2.5 gallons 110 leaded in his 1150).
I noticed very little to no difference.
Now on my F-7 and my friends stock m7's, there is a noticeable loss in performance running 91 octane.
We ride 7-10,000.