Octane number

[jcb986]

Originally Posted by Jamesp

So this is old school (literally) but I had a fuels and lubes course as part of my engineering degree, and we had a lab. The lab setup was half mad scientist, and half API testing rigs. a small part of the class revolved around determining, and changing octane ratings in gasoline using a knock engine in the lab. This was a big electricallty driven rig with a single cylinder, the compression ratio of the engine could be changed by turning a crank until detonation occured. Made a h3ll of a noise, all great fun (for engineers). The upshot was that experimentally, using the octane engine, the greatest increase in octane was not obtained with off the shelf octane boosters, but by mixing different octane gas (low and high ) from different producers. Why? Because at that time different chemicals were used to boost the octane in different brands, and the octane booster level in the gas was usually slightly in excess of what was needed so there was a little booster left over in each gas blend. Mix the gas blends together and you get a synergy that uses the left over boosters in each gas brand/blend to increase the overall octane of the mix you created. Because gas blends change constantly, as do the octane boosters, this is not reliably repeatable, but we were getting blends that were between 95 and 100 octane. There was an octane booster that claimed 101 octane that wasn't even close. I've made a point to use different brands ever since for higher octane.

I built street cars back in the 60's and I would mix premium American White 93 octane with Sunoco Blue Plus also 93 octane. These were leaded gasoline, anyway you could feel a change in how the engine ran and the mix also changed the smell of the coming out of the tail pipe. When I went to drag strip I would mix airplane fuel to gas. I was running a 327 Chevy engine, 12-1 pistons, polished and ported heads and high lift street Crane cam. My best guess was my octane was around 105. Engine screamed and it performed perfectly. If you are using racing fuel you would be disqualified. Racing fuel has very unique smell. So octane makes a big difference high performance engines.

[BYprodriver]

Originally Posted by jcb986

I built street cars back in the 60's and I would mix premium American White 93 octane with Sunoco Blue Plus also 93 octane. These were leaded gasoline, anyway you could feel a change in how the engine ran and the mix also changed the smell of the coming out of the tail pipe. When I went to drag strip I would mix airplane fuel to gas. I was running a 327 Chevy engine, 12-1 pistons, polished and ported heads and high lift street Crane cam. My best guess was my octane was around 105. Engine screamed and it performed perfectly. If you are using racing fuel you would be disqualified. Racing fuel has very unique smell. So octane makes a big difference high performance engines.

I built muscle car engines in the '80s & the best pump gas was Amoco 93 which was white/clear. If cylinder pressure was high enough to cause preignition or detonation I would add 130 octane low lead "blue" aviation fuel. Avgas lacked some lubrication additives that road gas has, so I also added Marvel Mystery oil. Experimented with the Cox model fuel & mothballs that were 100% Naptha. The Amoco 93 had a very distinctive exhaust smell, & so does the Avgas. I'm guessing the American White 93 became Amoco later.

[jcb986]

Originally Posted by BYprodriver

I built muscle car engines in the '80s & the best pump gas was Amoco 93 which was white/clear. If cylinder pressure was high enough to cause preignition or detonation I would add 130 octane low lead "blue" aviation fuel. Avgas lacked some lubrication additives that road gas has, so I also added Marvel Mystery oil. Experimented with the Cox model fuel & mothballs that were 100% Naptha. The Amoco 93 had a very distinctive exhaust smell, & so does the Avgas. I'm guessing the American White 93 became Amoco later.

Great, muscle cars where a lot of fun. American White was the best, but it is no longer the same because all fuels are now unleaded. The aviation fuel was fantastic add to the mixture, but you still destroy an engine if you weren't careful. Chevy man here. Owned a 55, 56, 57, 58. A 67, 68, 69 Camaro's. My new one off the lot in 64 was a Chevelle, built in June as a half year version. Had a 327, 300hp vette engine, Munice close ratio 4 speed and positraction. I changed the side flags to the 283 flags. So now I had a sleeper. Had a buddy with 64 Plymouth Valiant, 2 door and was the cheapest body style made. But, it had a V8, 4 speed and positraction too. Another sleeper looking for a pray.