Mutare23,

I'm no expert on the matter, but here's an excerpt from a discussion on the subject from the NSRCA (pattern) mailing list.

From Eric Henderson:

Ahhh! the wonders (or secrets) of engine behavior. Oil lubricates and
reduces friction to a point. But when included in the fuel itself it
does not necessarily cool. More fuel will cool.

The OS 1.40 runs so well on Coolpower because it has 17% oil. Higher oil
contents makes you turn the needle in to get more power and then edges
you towards "too lean" and the dreaded heat barrier. Less oil gives you
cleaner burn with the more volume of methanol and nitro present. The
heat is not removed by the excess oil. It does not burn nor does it give
any power.

Eric.

...
From Tom:
Great answer Eric, the increased methanol actually does the cooling.