what octane fuel?

[JSB]

what octane fuel do i need to run with 185 lbs. compression & possibly turning 10,000 rpms. engine is 300 drag

[Fl Boy in ILL]

I run 110 mixed with 93, at that compression I'd run 3 gal 110 and 2 gal 93.
I have a 300 drag with just a little more comp and I run 3.5 gal 110 and 1.5 gal 93.
Rick

[78Vector]

That compression ratio should run fine using straight 100LL Aviation Fuel (pump octane number of 100LL AvGas is actually 115)....around here that goes for approx. $2.70/gal, which is MUCH cheaper than mixing 3 gals of $4.75/gal racing 110 with 2 gals $2.35/gal 93 ocatane pump fuel.

[Riverman]

Do you have trouble buying avgas? Around here the dealers will not sell avgas out of the pump, they will only sell sealed drums from the distributor.

[JustMercMe]

Av would be good.....We just buy it at the airport here....just pull up to the pump and get what you need. Running around $2.79 a gal here.

[Mark75H]

I have no trouble buying AV gas in Edgewater (below Annapolis). The airport sells to the PWC racers with hopped up PWC's too.

Find the next closest airport .... unless it is a Canadian thing

[78Vector]

I have 2 small "local" airports near me that have "pay at the pump" credit/debit card readers just like normal gas stations that are open 24/7.
I have been paying anywhere from $2.50 to 2.75/gal for the last 6 mos.

[GesseR]

Would it be worthwhile or any advantage to running an avgas mix over high test even with 125psi? i run premium all the time anyway and thats close to the same price.

[Dutch]

GesseR, too much octane and it wont burn, it will slow you down.
I must mix on the light side after hearing all your mix ratios. I run
215# of compression, and mix two gallons of 93 to one gallon of
114. This puts me at 100 octane, and I spin 9500 rpms, I havent
had any high egt temps or detonation problems. I do spin a prop
that has a good bit of slip. Maybe Im messing with a time bomb
here with my level of octane.

[Jay Smith]

At 185 # cranking compression with 25 degrees timing and at sea level you would be super safe with the 3 gals of 110 racing motor gasoline to 2 gals of super unleaded pump motor gasoline...........

The timing and the altitude make a difference..........

Good luck,