98 Octane Unleaded Fuel?

[Zektor]

Hi,
In the UK, Shell has been selling a fuel called "Optimax". It's octane rating exceeds 98 RON. I have an '82 Corvette and have used this fuel on occasion. I have noticed a slight difference in performance... but I feel that I might not be getting the best out of the fuel due to the ignition timing in my Corvette.

Question1: What is the standard ignition timing for an '82 Corvette and what fuel was intended for the vehicle at production?

Question2: If I use 98 RON fuel. Can I adjust my Corvette's timing to get the best out of the fuel but not to much for the car to start pinking?

Question3: What would people recommend I set the timing to in my Corvette to get the best out of this fuel?

Cheers
Dazza

 

[Ken]

First of all, we're talking Research Octane Number, correct?

In the late 1960's there was a controversy between the U.S. Federal Trade Commission (FTC) and the U.S. refiners about posting octane numbers on gasoline pumps. The FTC wanted RON's posted. The refiners objected that RON didn't tell the whole story. The FTC considered posting RON and MON. "Too confusing," said the refiners. The FTC finally arrived at a compromise by ordering the following be posted on gasoline pumps: RON + MON / 2 That measure doesn't have any particular meaning other than the fact that the controversy was over.

The second piece of information about octane numbers is how they behave. When two gasoline components are mixed together, the RON's and MON's do not blend linearly. That is, the resulting RON and MON is not the volume averaged octane. However, and most fortunately, there is such a thing as a blending octane number for the RON and MON of every component which does blend linearly. The blending octane number is related to the true (test engine) number in a constant way, and is developed by experience. When references are made to RON's or MON's of components, they can mean either true or blending octane number. Hereinafter, all references to octane number will mean the blending octane number, not the true number.

So, if I read the post correctly, they are selling gasoline based on the Research Octane Numbers (RON) alone.

For more insight into the refining and blending processes behind the manufacture of gasoline, see the gasoline articles in the Mod-Shop columns.