100 Octane

[Ken]

All I know is there wasn't any lead in the fuels we blended for sale in California. That's not to say that there is no leaded aviation fuel. As a matter of fact, Chevron does still blend Avgas with lead at other refineries:

Antiknock Additive

The most important avgas additive is tetraethyl lead. It is added as part of a mixture that also contains ethylene dibromide and dye. Ethylene dibromide acts as a scavenger for lead. When avgas is burned in an engine, the lead in tetraethyl lead is converted to lead oxide. Without a scavenger, lead oxide deposits would quickly collect on the valves and spark plugs. If the deposits become thick enough, they can damage the engine. Ethylene dibromide reacts with the lead oxide as it forms and converts it to a mixture of lead bromide and lead oxybromides. Because these compounds are volatile, they are exhausted from the engine along with the rest of the combustion products. Just enough ethylene dibromide is added to react with all of the lead. However, because the reaction does not quite go to completion, a small amount of lead oxide deposit is found in the cylinders of aircraft piston engines.

For more reading on the properties of Aviation Fuel, see Chevron's technical review on Aviation Fuels.

 

[G Winter]

WOW! what a can of worms that opened..... Guess I should have added if you have your cats removed.

 

[WhalePirot]

All the '87 emission gear is installed and working, including a stock '84/5 cat, air pumps, diverter valves, etc. It passed CA SMOG visually and at the tailpipe.

A few CAC members and a few local Corvette professionals know what an animal this car is. The 100 octane purchase was solely due to my curiosity and, that stated, I have no intention of doing it again.

Hey, Mic. I was teasing. The Brits say anti-clockwise, not counter clockwise. I heard your meaning.

P.S. I don't buy 91 octane for my cars that run fine on 87, either.

 

[Mad-Mic]

P.S. I don't buy 91 octane for my cars that run fine on 87, either.

i do just cause i'm dumb :L don't need no knocking i drive

 

[Hib Halverson]

I worked at the Chevron refinery and we blended Avgas. After the lead ban went into effect, there is no longer any lead in (California) gasoline; not in any aviation nor in any motor gasolines. Zero, zip, zilch, nada... No lead whatsoever.

I'm sorry, Ken, but you're wrong.

Federal law mandates unleaded gasoline for use in all road vehicles but not for aircraft.

Go to any airport in the LA area and you'll find AVGAS 100LL, 87 and 100.

 

[Ken]

Okay Hib, my old brain ain't workin' as good as it once used to. I had to call in when I saw this just to refresh my memory, and you're right. We quit blending AvGas here in the LA basin back in the mid-nineties; Richmond and Pascagoula, MS have blended all of our AvGas since then, so they do still add lead to aviation fuel.

My mistake, but is has been ten years since I last blended fuels, and I'm not gettin' any younger, nor is my brain.

When I started at Chevron, we still had the purple 145-Octane AvGas.

 

[WhalePirot]

I have tried the 100 octane mixed with 94 octane several times in my '82(back when I could afford to waste money). Just enough to get it up to about 96 octane average. The detonation rate is significantly reduced to the point that I could hardly hear the engine running.

I think this states, very well, how this engine runs,now that I have a few more miles on. I was wondering if it was my imagination.

Much grass, to all.

 

[1995vette]

Octane does not make power it is simply a number given to fuel on how it resist detonation the energy content of the fuel is what makes power and some chemicals produce more than others unfortunatly alot of these power making chemicals have very low octane numbers therefore lead has to be used. Most people do not know the difference between Research octane and Motor octane and how these numbers are arrived at. These numbers are produced on an octane motor these motors are single cylinder engines hooked up to an electric motor to keep them at a steady rpm, you can raise or lower the head to increase or lower the compression while the motor is running these are big,old expensive machines. The standard used to set the machines up with is pure Isoctane for numbers below 100 anything above 100 lead has to be added to the standard. Then they run the fuels to be tested and compare. Below is the difference between the two.
Research Machine

RPM 600
Timing 13 BTDC
Intake Air Temp. 120 F

Motor Machine


RPM 900
Timing 26 BTDC
Intake Air Temp. Heated to 300 F

BTDC = Before Top Dead Center

You can see which of these two machines puts more stress on the fuel. The motor machine is ran at more rpm, double the timing and the intake air is heated therefore it more closely represents a racing application and is more important than the research machine because it stresses the fuel that is why the motor number is always lower than the research. When comparing fuels always compare the motor number it means more because some fuel companies advertise the research number because it is higher and lookes good to someone who does't know any better.