Technical Aviation fuel, should I be using it?

Dad made the mistake of putting ethanol in his 36 1.5T and let it sit. I had to disassemble the old Stromberg carb and clean all of the corrosion it had caused. It wrecked the inside of the carb. Took me hours to get it all cleaned out. Never again.

 

Nevermind that using aviation gasoline in a street driven vehicle is a violation of state and federal laws.

No big deal that both you and the airport can face hefty fines if you get caught.

If the airport gets caught more than a few times, it can have its permit to store, sell, and dispense fuel revoked.

Small price to pay, right?

 

The plural of anecdote is not data.

I have been running it in everything (that is diesel or propane fueled) since MTBE went out-of-use.

European, Asian, American, old, new, carbureted, EFI, with just about every single make of fuel system.

I have yet to experience an issue.

I have had more than 300 cars through my shop in that period. Probably 75 bikes, too.

I refreshed the carburetors in my R100 GS/PD before I sold it. It had 268,000 miles on it, with about 165,000 of those running on E10.

The carburetors were still fairly clean inside.

 

First offense by a end user is a $1,000.00 base fine, plus $10/gallon.

Fines increase with repeat offenses.

Beyond that, every owed state and federal road tax that was not paid.

 

I run e10 in my daily drivers with no problems. I think there is two basic problems with e10.
1. Ethanol attacks some rubber type seals, hoses and diaphragms but I believe most newer stuff uses materials compatible with ethanol.
2. E10 has an affinity for water, and when left in steel gas tanks, lines etc for longer periods of time causes rust.
I have dismantled small engine carbs that sat for a long time with e10 that had a lot of rust in the bowls.
I personally run non ethanol gas in my small engines and in my older cars. The cost is a little higher maybe 50 cents to a buck more per gallon.
The last small engine I bought from harbor freight has a sticker. So they must have upgraded components.

 

It's an urban legend that higher octane burns "slower" and I've also heard the wives tale of still burning and killing valves. Nope. Yeah, I said it...

 

Yeah, these persistent myths won't die.

 

After reading the posts above by Gimpy and Highlander, both of whom I respect because of past posts; I spent some time with Google.

As to the valves burning: I had never heard this, and don't know (and really don't care).

As to the slower burning of high octane fuels: I have heard this my entire professional life, and have solved a LOT of customer problems (power, and fuel economy) by having the customer convert to lower octane fuels on lower compression (5 to about 9.5) engines. Yes, I have quite a few customers with older engines with a compression ratio below 8:1.

So, after reading from several different websites (including those from some petroleum producers) it appears that some higher octane fuels do, as I thought, burn slower. But others, specifically designed for racing, can burn much faster than lower octane street fuels.

So unless one can actually obtain the fuel specifications on the specific fuel one is buying (good luck on that at the local airport, or gas station) one really isn't going to know for certain.

Thus, I will amend my post about possible issues to read that the higher octane may or may not burn slower.

Thank you Gimpy and Highlander for forcing me with your posts to do some research! One of my favorite quotations belongs to Will Rogers: Roughly "it ain't what you don't know that hurts you, it's what you know that ain't so!".

Jon

 

On a similar note, years ago people started using Av gas in their race cars and hot rods simply because there was no high octane racing fuel commercially available at that time. Today, I’m pretty sure you would be better off using racing fuel vs. Av gas if you have a high compression engine.

 

There is some truth as to lead protecting valve seats from receding but I don’t believe that anything in the normal gasoline grades from AV gas to e10 87 octane will cause a valve to burn as long as AF ratio is in the ball park.
Lead builds a barrier between the valve and seat slowing or stopping the microscopic welding. Large industrial 4 stroke gas engines run a medium ash oil to coat the valves and seats which extends valve life. The only valve I ever burnt was in a 350 Chevy pulling a heavy load in a head wind basically WOT in -20 degree weather for a lot of miles like 600 or 700 miles.
Dan

 

WOW! Some really indepth information guys. Keep the good words coming and thanks for the input.

 

I knew a guy who put it in his truck and said it ran like crap. I think you need pretty high compression for it to burn correctly. Dont trust what I say, I'm a bodyman and engines are not my expertise.

 

Gasoline engines rely on the combination of spark and compression to ignite the fuel.

Higher octane fuels are intended to reduce the chance of compression ignition in higher compression engines.

If you put very high octane fuel in a comparatively low compression engine, the contributing factor to ignition that comes from compression is negated by the higher octane.

Under those conditions, only the spark is igniting the fuel.

This decreases efficiency, especially if the ignition system is marginal.

So yes, very high octane gasoline in a comparatively low compression engine can harm performance, at the extreme ends of the spectrum.

 

Fuels are pretty optimized for the intended use. Avgas is optimised for the working conditions of an airplane, which can include conditions such as low air pressure (affecting how the fuel vaporizes) and quite low temperatures.
Avgas is indeed a relatively poor choice for a race car, compared to some other race fuels, unless perhaps if you intend to race around the peak of Mount Everest. The fuel just happens to be a better option than regular pump gas, and it was actually available. It's far from the best theoretical option for a race car, but as the market for racing fuels is very small compared to something like fuel for piston engined planes people has had to make do with what was available. Few refineries would bother to develop a race specific fuel that will only sell in very small amounts, when they can take the avgas they already produce loads of and slap a sticker on the barrel/can saying "race fuel" and sell it for more money than the same avgas at the airport.

 

Every vehicle I’ve ever needed high octane fuel for needed large quantities as well. If you’re using aviation fuel to dilute and raise octane of regular fuel, there’s better ways to do it.
https://race-gas.com/

 

The problem of water can be easily corrected.
My neighbor is an airline pilot and motorcycle rider.
He fixed me up with this.
Go to your Harley Dealer and ask for a bottle of the 'stuff that removes water.'
You want the larger bottle $29. A little goes a long way.
Proven to remove water from gas.
Yes he told me the name, and yes I have bought it a couple times.
But the name alludes me now, CRS: when I get to the shop I'll yell it out.
Anyhow Harley Users often park for extended periods and being plagued with the, system
water contaminant, found it to be the answer to the misery.
Works for me. Last time I went without the name in mind they knew what it is.

 

Av gas should be 100+ octane and yes will contain lead. I say use it if you can get it easily as it seems you can. Lasts a lot longer and will be better quality than any pump gas, probably won't improve the performance of your engine without increasing the compression ratio but sure smells great. Nice 900 there too.

 

I need to produce my Racing License and a Race-Car Log Book to buy Avgas [Yet I can't trailer my Race Car there and pump it straight in, it must be in a container]
Avgas is slightly cheaper than 100 Octane pump gas in NZ because there is no road taxes factored into the price.

The smell has a narcotic affect that makes a tedious chore like mowing lawns bearable .
When I start "apexing corners" with my lawnmower then I've been sniffing too much

 

....Thanks. I'm the original owner.

 

That why if you run it, and pay the price for it , you should be blown with BOOST! LOL.

 

My 1946 John Deere Series H had 4.75:1 compression.

The Garrett T03b made it scoot!

 

Strictly personal experience. Never had a corrosion issue until this point, then all of a sudden we have a problem. Coincidence or just an evil gift from the hygroscopic demons? Never used it since and no issues, draw your own conclusions. Not a scientific study and no animals were harmed during this test. Your mileage may vary.

 

AV gas smells better than CAM 2 , ain't nothing like the smell of good gas ! the slop they sell today is just barely gas.

 

I used to run AV gas in some high compression street cars over 40 years ago... we had to take in a couple of Geri cans and someone would help us with the fill, no cars allowed on the tarmac. One day a guy asked what are you using this for and I sheepishly said for my High Performance car! This guy was one of the mechanics at this little airport and said this- This gas can be used with standard pump gas but it is designed for engines that run at high altitude 10,000 to 20,000 feet at a constant RPM the opposite of a street engine that is in and out of the throttle all the time. I learned that it was pissing away extra cash so if you run a pretty standard street car it is wasting money. Look on VP RACE FUEL SITE they sell approx. 15-20 different performance fuels for every engine use, granted it is not 7.00 per gallon it will be 22.00 dollars a gallon and up but your engine will love it if it needs it! I am not a chemist but an engine that is guzzling a higher rated fuel then what the engine needs, is just pissing those hard earned greenbacks down the drain.....

 

Yes. The downside is that you're spreading a highly toxic pollutant. There's no safe level of exposure to lead.

 

What I have not seen addressed is, does AV or Rec gas have a higher boiling point than regular pump gas?

In Chicagoland, I have to deal with fuel boiling in carbs on a pretty regular basis.

What changed in pump gas formulations over the last 10-15 years that has lowered the boiling point?

We rarely if ever had this issue before then, other than in Rochester FI systems where the fuel would boil and vapor lock in the spider lines at low RPM.

Case in point, two days ago, had a car flooding after shut off hot ( fuel dripping from boosters)
I was performing a wet float adjustment on a Autolite 4100. One of the probably very few carbs that the engine can be run with the top off of the carb.

It was 99 degrees here in Chicago. Engine was up to operating temp. Ended up lowering float levels way below specs to try and stop the problem.
Fuel was fresh premium pump gas.
The float levels are probably low enough now, that it probably will starve for fuel at WOT, but doesn't seem to be pushing fuel out the boosters during a engine off hot soak.

After shutting down the engine, after a few minutes, the fuel started to boil in the bowls.
I took my temp gun to the fuel in the bowls and it read 190 degrees. I believe my temp gun is pretty accurate.

Wish I took a video of it happening.

Carb has a factory 1/2" phenolic spacer now and can't go any taller due to hood clearance.

This boiling issue and also the fuel volatility seeming to go south in a few months is a real problem around here.

So how the #$%& am I supposed to fix this? Tell the owner he's has to fuel injection the car?
This is bullshit!

Guy takes his classic carbureted car to the taco stand, car sits for 15 minutes, he goes to start it to leave, and it won't start. First thing he does is pump the gas and try again, still won't start because he flooded the engine even more. Then it gets towed to me.
Then I have to try to find a way to fix the issue, where sometimes there is just no way around the problem.

Hell, my flathead has a fuel pump with a glass bowl and the fuel will turn piss yellow in the bowl in 2 days. Gas in the tank seems to stay clear longer. Maybe that has something to do with heat and a small amount of fuel. Doesn't matter where I get the gas from. Didn't do that 15 years ago.

I'm done with my rant.

Bill

 

If your car doesn’t have the compression ratio to need it your wasting $$ you could be buying parts with .

My 70 Cobra 13:1 from Ford . When you pulled down the plate to fill , sticker said : Use minimum 110 or greater octane or serious engine damage will result voiding factory warranty .

My Buddy worked at local airport , fuel tanker pumps . He would call me , “ meet me at gate 4 , 8:00 o’clock . I have fuel to dispose of to empty the tanker . I would stop by , he would fill it up until it ran out on the ground . I hit the road and happy for a week .

When I couldn’t get blue gas , 260 Sunoco plus 3 bottles of 105 octane boost , the 429 SCJ would laugh at you and rattle like two skeletons , gettin after it in a tin can .

 

Not sure what exactly changed in the gasoline formula I do know that today’s gasoline doesn’t have as much iso butane as it did way back. Butane was reduced because it would vapor off causing some pollution , maybe something was done to lower the boiling point allowing gasoline to vaporize easier - just a thought- Have you tried non ethanol gasoline?
Dan

 

Had an opportunity to to bs with a fuel system engineer from Ford. In simple terms hydrocarbons have heavy and light ends. The light ends are more conducive to becoming more aerosol for more complete burn and effective delivery from injectors. In the northern parts of the US all the pump gas has more light ends than heavy. Better in cooler regions where heat doesn't aid injector function. Ethanol has a cooling effect and in constant use absorbing water is a good thing. The downside is the boiling point you're dealing with. It's possible that some additives may introduce more heavy HCs. Maybe year-round Sta-Bil, Lucas, etc. The lubricant in such products is also welcome. Could be a cheap reliable solution.

 

Maybe we should do a rethink on our engine combination because you can build a thousand horsepower on pump gas today, it seems there should be no need for a high octane, leaded fuel.