Octane Supreme (formerly Lead Supreme)

[Chevy454]

That's a good point, Sam...99% of the folks out there have no idea what their *actual* CR is...unless you cc everything you're just guessing. I'd say the vast majority of the engines out there are well below where their owners think they are. And while running too much octane isn't as physically detrimental as running too little, it *will* hurt you performance-wise, and make your car temperature sensitive...been there, done that!

[mockingbird812]

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That's a good point, Sam...99% of the folks out there have no idea what their *actual* CR is...unless you cc everything you're just guessing. I'd say the vast majority of the engines out there are well below where their owners think they are. And while running too little octane isn't as physically detrimental as running too much, it *will* hurt you performance-wise, and make your car temperature sensitive...been there, done that!

[/ QUOTE ]

Rob,
For what its worth, I have receipts from local shop which performed recent engine rebuild including specs on L78 pistons and have decent confidence in what my CR is. I am not sure I understand your comment: "And while running too little octane isn't as physically detrimental as running too much". I thot that running too little may lead to detonation which could be quite damaging to the pistons. I thot there was more room for error on the top end, i.e. too much octane was more of a waste of $ vs. potentially damaging.

[Chevy454]

Sam: you're too quick! I re-read it and realized I had it backwards (too early yet)...and wasn't pointing the finger at you directly...sorry if it came across like that!

But like a lot of folks, I used to *assume* that since my L72 was rated at 11:1, that it would in fact be close to 11:1...WRONG. I tore it down, did an ever so slight clean-up on the block & head surfaces, and put a set of TRW blueprint 11:1 pistons in it...then I broke out my cc'ing kit, and my jaw hit the floor...I had a WHOPPING 10.2:1 compression! Quite a far cry from the advertised 11:1 I was expecting, and this was after removing some metal and getting (what I thought was) a good set of pistons. I did some asking around, and it turned out it was common...Scott Tiemann had done a similar experiment on a Berger COPO, and came up with 9.8:1!!

Anyway, running in Pure Stock I saw everyone else at the track dumping in race fuel, so I automatically did the same...but I was at a T'n'T one night at MMP, and the car wasn't as sharp as I thought it should be. It was late summer, and had cooled off a bit (cool for Memphis, at least, which is my home track), and it finally dawned on me that I had mostly race fuel left over in the tank from Stanton. So, I pulled it out, put in some good ole 93, and ran a 12.7x (about .05+ quicker than before). But I've also hurt parts with too little octane...busted the ring lands off of a 454 I was cutting my teeth on in high school...all lessons learned.

[mockingbird812]

Rob,

No, I didn't feel you were pointing fingers. Yours was a good point, that is why I started off with, "For what it is worth..." (obviously not worth much unless you take actual measurements).

So any rules of thumbs that you use? i.e. when the moon is in the 7th house, and Jupiter aligns..... I use XX octane.

Thanks,

[Chevy454]

A rule of thumb? Keep a close eye on your plugs. I was never a fan of octane stuff in a can because it colored my plugs funny and made 'em hard to read. It's definitely better to err on the side of caution, though.

[tirebird]

I've been using it for some time now. Before rebuilding the LS6 I used it in any tank of lousy California ethanol diluted 91 octane. I wouldn't use it when I filled up with 100 unleaded or 110 leaded at the local track. Now that I've rebuilt the LS6 with 9.5 c.r. heads/pistons, I don't use it that much. However, when I do throw a bottle in, even with the lower compression, my SOP feeling is the car is more responsive and powerful. But that's not science, just my impression.

[mockingbird812]

Just returned from AZ emissions station this a.m. with the subject car. I filled the tank prior to this with one quart OS 130 and the rest with 91 Octane gasoline. According to the Kemco chart my 18 gallon tank with 1 qt of OS130 shld net a 5 point octane rating gain or 96 octane. Car ran beautifully and strongly and I passed the emissions test loaded and at idle for HC and CO. Will monitor plugs and performance as the ambient temps increase. I don't put many miles on this car.

Thanks for your inputs.