I raced today in Fayetteville Motorsports speedway and I tried three gallons of the 107 octane race fuel mixed with about a gallon of 93 that was already in the tank. I used the 100 octane tune, My times where worse than with the 93 octane fuel and tune. what has been your experience?

Should I contact my tuner and have them check the tune? or forget the higher octane fuel all together?
there was a little detonating sound around the 1000 ft mark.

 

Say what? If you had detonation with 107 then you might need to check your plugs and tune. Did you try your 93 tune and still get the detonation?? or maybe they sold you water.

 

I always heard that 107 is leaded fuel and you should only run it if your engine can take it. You would most likely need a tune for 107 if you use it but I don't see how your times could be worse.

 

All the Sunocos around here have 100 unleaded at the pumps

 

You lucky dog...

 

Leaded racing fuel will ruin you O2 sensors and catalytic converters, if you have them, in a hurry. I rarely trust track fuel if it is stored in above ground tanks. High octane fuel will only benefit your car if your tune was written for it i.e. more timing. I suggest and use VP fuels MS 109 octane unleaded fuel. 104 octane unleaded fuels are fine as well. I'd only use unleaded race gas if my car was tuned in open loop and I had no cats. Then why not run C16 117 octane leaded?