I was trying to remember, was 109 the highest you could select at Sunoco when they had those dial your octane pumps?

I remember a customer in the mid 60's at Caldwell Airport( now Essex County) NJ that bought either 100/130 or 115/145 octane aviation fuel for a big block ford that he raced.

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Jeff

97 E320, ours 217,000miles
91 190E 2.6 daily driver 242,000miles
74 MGB,mine 120,000?
2006 BE350/Proline 21, 50 hours

Some Unocal stations in CA sell 100 octane unleaded race gas from pumps, but, I didn't know that a similar fuel was available from Shell.

The current 100 PON is equivalent to a 104 to 105 RON fuel from the sixties, so it would be okay for an L-88 Corvette, which had a CR of 12.5:1 and required a minimum of 103 RON.

Duke

Catalytic converters & O2 sensors need NO-lead fuel. "Low" lead will kill 'em.

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Norm in NJ
Next oil change at 230,000miles

It might be enriched ethanol blend.
Here in Iowa and Minnesota, some stations sell 100+ octane that is 80-90% ethanol.
And it’s usually as cheap as regular gas - $1.80/gal.
Just remember that octane is not a rating of power, rather it’s a rating of the ability to burn. I.e. high number = easier to burn.
Also, ethanol has a lower power by volume factor than plain gas. Your engine will not miss but you will get less miles per gal.
FYI, diesel has the highest of common fuels: approx 160k btu/cc vs 140k btu/cc for gas.

FWIW - I sell hi performance gas (110 Octane Sunoco, $5/gal), and build race motors (for motorcycles).

High octane fuel is only appropriate with very hi compression motors - if you put it into an engine which runs well on 91 Oct pump gas, it won't help anything (maybe slightly lower cyl head temps), and will most probably result in a decrease in power.

Most engines make the most power with the LOWEST octane which will burn clean (no pinging, knocking).

I have won lots of races (literally 100s) running 89oct pump gas in "factory stock" motors.

-David

ps - Yes, any "leaded" gas (low-lead included) will ruin cat converts.

Also, I imagine that if you tried to buy gas out of that pump (100oct Race Fuel) then they would tell you it has to go into a container (or a boat), and that you cannot pump it direct into your car.

There was a run of "exotic fuels" a few years ago in the motorcycle race circuits and the popular stuff was ELF. It was rated at about 105oct, cost about $40/gal, but it was something other than "gasoline", (there is a test for specific gravity,and if the "fuel" passes, you can run), and if you got near an open container it made you feel really sick, BUT it resulted in a few horsepower (in built motors - stock motors just ran "crisper", possibly better throttle response but no real increase in power).

-David

Jeez - the current EPA limit on ethanol concentration (by volume) for pump gasoline is 10 percent, so any oxygenated gasoline dispensed from a gas station as motor fuel for on-road vehicles is no less than 90 percent gasoline. An automtive engine designed for gasoline or "gasohol" with a small quantity of ethanol will not operate on a high concentration of ethanol due to the substantially different A/F ratio, which would require considerably higher mass/volume flow of fuel.

Octane rating is a measure of resistance to detonation. That's it! It doesn't burn "slower" in the absence of detonation. If an engine operates without detonation on a given octane, then additional octane DOES NOTHING!!!

Ethanol is an octane enhancer, but has less energy density, so base stock gasoline oxygenated with ethanol has lower octane than a base stock not intended for oxygenate addition. Ethanol brings a base stock intended for oxygenation up to the pump posted octane. Also, ten percent ethanol reduces the energy content by about 3 percent so fuel consumption is increased by about a like amount.

Duke

In AZ I can understand slightly higher octane . . . it's actually the heat and humidity levels that can affect engine performance.