Aviation Gas

I know some on the forum use aviation gas (100 octane) for their small engines. I read today in a general aviation magazine that the FAA is going to phase out the current formulation by 2016.The reason? Not what you expect! It does contain lead and the EPA has concerns but the real reason is that their is only one maker of the lead additive in the world..and they"re considering discontinuning it as it is a very small market. Shell among others have been experimenting with other addititives and "think" they can get all the benefits of lead with other propietary formulas. It would retain the 100 octane rating. Thought you might like to know.
 
2,2,4-Trimethylpentane is 100 octane AKA Iso-Octane.

When I worked with AVGAS, DuPont was the maker of lead additive TEL (Tetra Ethyl Lead).
 
This gets me to thinking, when we raced stock cars, we added an octane booster to our gasoline. Can't remember the name of the stuff, or how much it boosted the octane, but a quart was $8.00 or so and did ten gallons of gas.

(The rules said "pump gasoline only", but everyone had their own formulas).

Wonder if they still make it. Although all of my small engines run fine on E-10.
 

Goose- This is what I used in the early '80's...


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They have been talking about this for years. The liability issues from changing the formula would be staggering. Don"t look for it to happen anytime soon.
 
(quoted from post at 04:04:14 02/11/14) 2,2,4-Trimethylpentane is 100 octane AKA Iso-Octane.

When I worked with AVGAS, DuPont was the maker of lead additive TEL (Tetra Ethyl Lead).

That's correct. I worked with aviation fuel for 25 years. Lead, blue dye, and high grade gasoline. Would make temp. corrected specific gravity 100 octane.
Any chemical they try to add to replace the lead will require the total rework of the fuel system of every piston powered aircraft in the USA.
 
The reason for using avgas has nothing to do with lead content or high octane. Modern small engines need neither. The main advantage of avgas is its long-term stability. Avgas has a maximum Reid Vapor Pressure of 7 psi, primarily to prevent vapor lock. Historically, mogas had a much higher vapor pressure, but typical summer grade gasoline sold today has a relatively low RVP. In some areas, summer grade gas is limited to 7 psi RVP, same as avgas. In California, RVP is limited to 7 psi year-round.

A lot of companies are working on replacements for Avgas, but the real problem isn't replacing the lead so much as is the small market for aviation gasoline. There's not a big incentive for companies to come up with a replacement for a product that's not a major part of their bottom lines.
Local Reid Vapor Pressure requirements
 
>Any chemical they try to add to replace the lead will require the total rework of the fuel system of every piston powered aircraft in the USA.

That is nonsense. The fuel system doesn't care if there's lead in the fuel or not. The engine only cares if the octane is sufficient, and 100 octane is overkill for many engines. There are thousands of aircraft flying today with auto fuel STCs; many of them have been running mogas for over twenty years. There are thousands more experimental aircraft running auto fuel that don't require an STC to do so.
 
The primary advantage of Av Gas is that it doesn"t gum up or varnish fuel systems. That is why my seasonal equipment is filled and ran a little while with 100LL before parking.
Other than some cantankerous P&W radials , few aircraft engines require lead.
As previously stated the concern is Reid pressure. Who wants a vapour locked engine when at altitude. Although most piston aircraft never exceed the altitude where oxygen for the pilot and Reid Pressure is a concern.
Carb icing is another problem but that really isn"t a fuel problem. Other than wanting lots of octane when at full throttle while carb heat is on. Once at cruise most aircraft engine most reciprocating aircraft engines would run ok on 87 octane.
Problem is the logistics of carrying high and low of tanks of fuel. It ain"t practical. So fill"er up with 94UL or 100LL.
 
I have used VP gas a few times in older gas tractors and have ran some in air cooled engines. Exhaust got white looking like back in days of leaded gas.
 

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