Octane Calculations

[socal pat]

For those of us who live with 91 oct. can someone (TOM) :wink: give us the formula for figuring the ammount of adder to raise octane by 1, and 2 points....given, let's say, 10 gallons of 91 fuel and 101 oct as the adder?
Thanks

[raceskier]

Pat,

As far as 91 octane gas , I feel your pain.

Combining different octane gasolines will follow the rule of mixtures. Say 5 gallons of 91 and 5 gallons of 101.
5 X 91 = 455.
5 X 101 = 505.
455 + 505 = 960.
960/10 = 96 octane.

Now adding toluene or some other concoction, you will need to know their R+M/2 octane.

[chuckerants]

So I guess 2 gallons of 101 = 93 octane?

[socal pat]

Or 10 gal. of 91 and 2 of 101 will fill me up with 92.6. That's probably good enough for a 110mm pulley in 103* heat. Thanks guys.