<VV> 100 Octane Fuel

[FrankCB]

Dave,
     If you are NOW retarding the ignition timing to stop pinging, then running a higher octane (OR going to water injection) will enable you to restore the timing to normal, thereby gaining both power and mileage.  If it's only 20 cents more a gallon that's probably only about 5% more $ and your mileage will likely improve at least 5% so the increase in power is a bonus.  But you will have to change the timing to achieve this.
     The 150 and 180 turbo engines were designed to run on leaded premium which was probably a higher octane than the 91 you are presently using.
     Let us know what happens if you make the change.
     Frank Burkhard

In a message dated 08/27/08 21:07:55 Eastern Daylight Time, dave.thompson at verizon.net writes:
I just found a gas station in Ontario, California that has a separate gas 
pump that dispenses 100 octane fuel for about 20 cents more than their 91 
octane premium. It is about 40 miles from my home. That got me thinking. 



I have the timing retarded on my 63 spyder to stop it from pinging on 91 
octane. I'm guessing that if I run the 100 octane I could advance it a 
little. If I ran 100 octane without changing the advance would I see 20 
cents a gallon's worth of extra performance or would I have to change the 
timing? To be honest, if there is really no advantage without changing the 
timing, to me, it's not worth changing it. Would there be any advantage or 
disadvantage to running a tank of 100 octane now and then? Would there be 
any problem mixing a partial tank of 91 with 100 octane? I bet not, just 
less than 100 octane performance. 



A buddy of mine usually uses 85 octane in his Piper Cub airplane. However, 
now and then he can't get it at an airport he is visiting. When he uses 110 
low led avgas he says that he sees a noticeable difference in engine 
performance without making any engine adjustments. Is mixture control 
considered an adjustment? By the way, he does have an STC for auto fuel use. 




If it will give me a little boost in performance, I'd like to "give the dog 
a cookie" every once in a while. 



Is there a website that lists gas stations that carry 100 octane?