Any studies done on pump fuel quality ?

[Kern Dog]

I am curious if there have been any tests to determine the quality of the fuel we buy today. I hear people claim that the 91 octane we have in California isn't really a true 91 rating, but what criteria is used to arrive at that conclusion? The department of weights and measures are responsible for the verification of the pumps, but who is in charge of fuel quality?

[Ghoste]

I think there are a couple of different ways to determine octane ratings and it affects that final number but I thought California used the same method as the rest of the US?

[deepockets]

so I hear that the octane on 91 is far less than that till they add the methanol. with separation between the two in the gas station tanks, you never know what your getting. I'm building something similar to yours and will be using a little race gas with every tank full for insurance.

[Kern Dog]

I'm building something similar to yours and will be using a little race gas with every tank full for insurance.

P L E A S E  take this advice: Be conservative with your compression ratio ! I am burned out on the detonation issue! A ratio of 9.5 to 10.25 is probably the limit for 91 octane gas.  Some will say that you can run 11 to 1 if you have quench. Maybe that is true but I'm tired of dancing in the mine field. Some guys say that a "bigger" cam will bleed off cylinder pressure at low rpms and detonate less. I worry that choosing a cam radical enough to do that may make the engine feel soggy at low to midrange.
Regarding the race gas: I built my car to go places, not just to race locally. My #1 goal is performance on pump gas. If you're okay with blending fuels every tankful, that is your decision. I am willing to give up a few HP to have a streetable combo.

[deepockets]

advice taken red. I got the heads back and now I'm going to match the combustion volume. I was shooting for 10.3 comp. thanks for sharing your story.