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Wow, where to start One persons 12 to 1 compression ratio can be a lot different than others, Cranking cylinder pressure is a better tool for octane number, we make 225psi with this engine @ 12 < not pump gas friendly> we made 185 with the same engine and different cam timing< pump gas friendly> The specific gravity of ave gas will be lower due to less water content in PPM for high altitude use, less tendency to freeze, I have never heard of ave gas made for lower RPM use and it is rated on the same scales as all gas fuels you can find both rating #s for the same fuel, all engines will preform differently at different rpms due to volumetric efficiency @ any given point in the rpm band, dynamic compression vs static, fuels are always an interesting topic , some times a lower octane fuel will prove to make more power in a situation where the burn rate is closer to the pressure needs of the cylinder than a higher octane fuel with a slower burn, All fuels of the same octane # dont burn @ the same rate< just to confuse things even more> I think most racers error on the side of higher octane to ward off detonation, and its probably a good thing, I would love to see more dyno posts comparing fuels in a controlled experiment so we can learn something new and end some of the fuel myths posts, I have read a lot of them and still have no clue if I have the right fuel for my set up

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Great post, awesome input!!!

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Dont ever let the highway patrol know you transporting or using av gas, its a tax thing law and it has lead in it.

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Probably same result as the diesel guys are having running number 2 diesel in their trucks. Last heard was $10,000.00 fine and than $1,000.00 per each gallon on the vehicle if they dipped the tank and had red dye in it. Was getting expensive for some. Plus not paying tax either gunna get the higher up people into it also. OOOOHHHHHHHHH it gunna get ugly. Some guys just said forget it and continued paying the high prices that were being paid at the pump. They didn't want the hassle. The little you save not gunna be worth it when greased up for what's coming if caught. Guys were even online saying they were doing it and telling everyone. Some guys spoke up and said "why you bragging it?" Now they know who to go too.

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I have never heard of ave gas made for lower RPM use and it is rated on the same scales as all gas fuels you can find both rating #s for the same fuel

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6.19 Are aviation gasoline octane numbers comparable?

Aviation gasolines were all highly leaded and graded using two numbers, with common grades being 80/87, 100/130, and 115/145 [109,110]. The first number is the Aviation rating ( aka Lean Mixture rating ), and the second number is the Supercharge rating ( aka Rich Mixture rating ). In the 1970s a new grade, 100LL ( low lead = 0.53mlTEL/L instead of 1.06mlTEL/L) was introduced to
replace the 80/87 and 100/130. Soon after the introduction, there was a spate of plug fouling, and high cylinder head temperatures resulting in cracked cylinder heads [110]. The old 80/87 grade was reintroduced on a limited scale. The Aviation Rating is determined using the automotive Motor Octane test procedure, and then converted to an Aviation Number using a table in the method. Aviation Numbers below 100 are Octane numbers, while numbers above 100 are Performance numbers. There is usually only 1 - 2 Octane units different to the Motor value up to 100, but Performance numbers varies significantly above that eg 110 MON = 128 Performance number.

The second Avgas number is the Rich Mixture method Performance Number ( PN - they are not commonly called octane numbers when they are above 100 ), and is determined on a supercharged version of the CFR engine which has a fixed compression ratio.

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100LL here in the states has a very low specific gravity, usually around .690. It also has additives to increase the shelf life to 18 months It was not design or intended to be ran much above 2700 RPM(burn time?) also so that seems to be a problem. I use to use the 115/1345 and when that went away we used the 115/130 octane. I found that all of my stock Mopar M.W. intake and exhaust valves where pitted after using that fuel for two years of drag racing only at or close to twice a month Needless to say I don't use it anymore in a high compression motor, I have mixed it with pump gas on occasion to improve the shelf life for sitting over the winter in cars that I don't drive in the winter I would not add any oil to any gas unless it was for a two stroke motor Alcholol race fuel is a different story

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Although some people seem to like AVgas in their cars that's not what it was formulated for.

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