Technical Aviation fuel, should I be using it?

Absolutely.

 

I'm thinking that the only issue is that you end up spending more money than you need to.

As far as gas breaking down it seems to break down a lot faster in tanks that are vented straight to the air through a vented cap or vent hose that doesn't run through a modern charcoal system or at least that is what my experience with a late model (08) rig we have has been. The gas in the tank on one of my trucks broke down in months while the gas in the HHR didn't seem to break down much at all. My daughter's old daily that has sat for quite a while that I am going to revive as a daily driver after a falling tree killed my daily. No hot rods or custom cars were involved.

 

In his book, The High-Speed Internal-Combustion Engine, Sir Henry Ricardo
mentions experimenting with Tolulene. He described it as "a pure Hydrocarbon".

 

Being on the coast its easy to find ethanol free marine fuel, its usual fairly low octane though. I use it in my bikes as they're more likely to sit for long times and oil doesn't tend mix as easy with ethanol blends.

I did the math one day. With the upcharge they put on the ethanol free fuel I should be able to go up to the distributor and be paid to take pure ethanol.

 

Don't use Jet A1 - unless you run a diesel!

 

The way I see it, the motor only needs so much octane and that's it. If a motor makes max horsepower on 87 octane going to 91 isn't going to or do anything to make it run any better.

If it needs 91 octane to run perfectly and make max power going to 96 isn't going to add a thing other than higher cost.

As far as sitting for a couple months, if adding gas stabilizer to it works then what else do you need ?

In other words, why spend a premium on something that's adding absolutely zero to performance, durability or gas milage ?

If it needs it-add it, if it doesn't- dont....

...

 

Yep, I've seen the dyno tests that prove it. If the engine makes as much horsepower as it can on 87, running higher octane does not change the horsepower number. If you have an engine that has the timing retarded to run lesser fuel then you can run higher octane fuel and put the timing to optimal to gain horsepower, but that's the only reason you would want to increase octane. Running 100 in something that runs optimally on 87 is just increasing the cost of what's coming out of your tailpipe.

 

Appreciate the responses everyone. Thanks.

 

A friend of mine uses jet fuel in his big kerosene heater. He says it's cheaper than kerosene and doesn't stink like diesel. He's a pilot and works on his own planes so nobody at the small airport he's at questions what he's buying or why.

Gary

 

My neighbor is a regular at the Av Gas pumps at the local airport. Burns it in every small engine, tractor and other gas engines he owns. He says he occasionally runs some thru some his gas powered drivers?

 

If it’s got a carburetor around here, it gets 100% pure gas. It costs the same as premium at the pump, octane is above regular but below mid grade.
My 99 F150 5.4 gets mid grade all the time, except when it’s pulling a trailer or loaded heavy, then it gets premium. It pings and knocks on regular. But the wife’s 05 Expy with the 5.4 will run on regular and never ping. But I still feed it mid grade. And I think her Jeep PentaStar V6 would about run on muddy water.

 

I use Avgas exclusively in my Racecar.
Any unburnt hydrocarbons are recycled in my lawnmower and line trimmer [both 4 stroke]

It is not recommended on anything with an O2 sensor or Cats

 

Hell no. Wouldn't want the animal cruelty crowd after you........ (Yes, yes....I know what you meant.)

 

I've posted this information before regarding octane rating so ignore it if it sends you into la-la land. My avatar has a 1950's engine in it. Standard form they had around 6.5 : 1 compression. Mine's possibly around 8.5 : 1. On a chassis dyno it put out a mind blowing 100 H.P.. The gentleman running the dyno told me to replace the 91 octane (Australian octane rating) with 98 octane. It dropped 10 H.P. on the next run. He was amazed. I told him what a retired oil company chemist told me. "98 is for computer controlled, injected engines because they slow burn the fuel whereas my old clunker needs bang for buck so stick with the lower octane".
When I replaced the 98 with 91 I instantly picked up the 10 H.P..

 

Been running it since '77 in the OT 12-1. Used to run it in my Sportster on occasion back in the 80s. At night, it would throw a blue flame about a foot out of the straights if you tapped down a gear and pinned it! Ridin' buddy's were quite impressed......

 

What people often miss is that the octane rating just is one property of a fuel. Different fuels also require different fuel-air mixtures (i.e. carb settings) and have different energy content, meaning burning a specific amount of it will yield different amounts of energy for the engine to convert into horsepower.

If you have an engine set up for regular pump gas the settings will be close enough for pump gas with a different octane rating from the pump next to it, but if you get a can of race fuel, aviation fuel or that low smoke stuff for lawnmowers you really need to go through all carb settings to adjust for the new fuel.
If you just go get some fancy fuel and pour it into something adjusted for pump gas there is no way you are getting everything that fuel has to offer. And don't forget trying different ignition settings to, the fuel may run far better with a different advance.

Methanol is an exaggerated example of the differences. It has a little more than half the energy content of pump gas, but it requires about half the amount of air to burn, so you jet the carb about twice as rich and the total amount of energy released is about 17% higher than pump gas (if I remember the numbers right). That's a potential 17% more power while still running the same low compression as on pump gas, increasing the compression to utilise the higher octane rating gives a further power increase.

You will not find such large differences between pump gas, race gas, avgas, lawnmower gas and so on, but there are enough differences for them to work differently, requiring different adjustments, and producing different results.

 

I used 100LL in the stock cars, beats the price of CAM2 at the track. I used to get it at a Beechcraft facility, not sure they fill cans these days. With my Ford, I wait until it gets to a 1/2 tank and pour in a can of VP octane booster. It raises the 93 octane to 97 or 98.

 

Is this cheaper out where you live? Here is the local price here in OK.

Fuel prices as last reported on 11-Jun-2024
100LL Avgas Full service $5.52 Reported by the FBO

Regular No ethanol is about $3.45 or it was yesterday when I filled up.

 

....That's definitely cheaper for the 100LL. I paid $7.00/ gallon here.

 

.....It's difficult to find no-ethanol here. Regular pump gas is about the same or a little higher here.

 

I’m going to go on record saying that ethanol in gas isn’t as big a deal as many make it out to be. I recently did an experiment. My boat had sat for about two years with the tank full of ethanol gas. When I went to start it, it ran poorly, so I assumed it had bad gas. (It turned out to have fouled spark plugs). I drained 15 gallons of gas out of it. I poured 5 gallons of the old gas into my 47 Chevy (which has a 350) to use it up. I drove it for a while, and it ran fine. I poured in another 5 gallons. After most of that was used up I poured in another 5 gallons of old gas. I now had probably at least 90% of old gas in it. It ran absolutely fine. I could not tell the difference. I know that modern gas evaporates faster than it used to, but beyond that I don’t see anything “bad” about it.

 

Back in the 80’s, a buddy had a hot 400 Pontiac I built for him. It was up to ram air four from the factory with the good at the time heads and a better cam. Compression was about 10.5 to 1 best I remember. Just cruising around, it would ping slightly on premium gas, not enough to worry about but you could still hear it at low rpm, like taking off from a stop sign in second gear and up shifting to third.

One of the mags of the day had an article on adding av gas for better performance. Had to bring your own jug or can, couldn’t just pump it into the car. We went in a pickup and got 10 gallons of the blue. By playing around with it, we found anywhere from 1-2 gallons was enough on his car, mixed with premium. It cut the quarter et as well as added mph to the top end, how much, I don’t remember. It was enough we won a few heads up grudge races, track and street. Wasn’t enough for him though, he couldn’t take the ribbing of gettin beat by Camaros with 327’s and 350’s. One guy even told him to put a Camaro front clip on his Firebird if he wanted to win all the time, lol.

 

You can look up ll100 prices here http://www.100ll.com/

 

Why not run the 98 with more compression and timing?
In fact, I'm quite surprised he didn't think to give the distributor a twist!


-rick

 

What's the reason you feel your Ford engine needs that high of octane? Is it high compression? Does it spark knock if lower octane is used?

 

The only problem running AV gas is going on line and telling the world, if you get stopped for a fuel check and they pull blue fuel out you now have a problem. They check trucks all the time here in NC for off road diesel. A buddy of mine used to run off road diesel until he got a 25k fine from a fuel check. Some things are better left unsaid .

 

All fuel loses octane over time. It seems like some hot rodder types want their car to need higher octane because it seems more impressive in their head. The reality is that if you don't notice a difference with old fuel in your car, the octane requirement is lower than what you normally feed it. Which is true for a majority of hot rodders. Regarding your experiment, was your boat fuel tank invented during your experiment? Degradation of fuel requires oxygen. If you didn't have exposure to oxygen, you slowed the fuel degradation significantly.

I did a rudimentary experiment a few years ago. My two-stroke push lawn mower had sat for a couple years with mixed fuel in it and wouldn't run. I drained some fuel from the tank onto a paper tower and lit it. It burned, but not with any volatility. I then mixed some new fuel and did the same. The burning of the new fuel had much more energy and was a hotter and faster burn. So I drained the tank, put the new fuel in, and the mower ran perfectly.

The below quote is taken from an interesting article from Sunoco. https://www.sunocoracefuels.com/tech-corner/article/octane-stability-high-octane-vs-low-octane-fuels#:~:text=Even in proper storage 87,decreases due to butane evaporation.

Ethanol fuel is a better cleaner than straight gasoline, which is why injector cleaner contains ethanol. Therefore you can end up with a rougher running engine because it's releasing crud from the system and clogging stuff up. Unfortunately, ethanol can also be more reactive with the rubber and other materials in the system. Ethanol also absorbs water where regular fuel does not. This is where the corrosion issue comes from. There's some interesting reading about it below.

https://roadguardians.org/ethanol/#:~:text=Straight gasoline starts to deteriorate,even faster than straight gasoline.

 

Somtimes these threads get "off content" (can't use "off-topic" as that would be for a newer post):

For the OP with two mild 350's, there is only one reason to use avgas: it is a more stable fuel.

Counter that with higher cost, LESS power (insufficient compression and timing for the slower burning fuel), and the possibility (although remote) of legal action.

EDIT: after research, the higher octane fuel may or may not burn slower. If your specific fuel does burn slower, then the engine may not operate at optimal efficiency, but the higher octane should not harm the engine.

Your call.

Jon

 

At least in theory if you run too high octane in a lo-po small cam engine the exhaust valves could get burned from fuel still burning. All sorts of stories about Jeeps in WWII burning the valves when avgas was used in the engines designed for what today would be very low octane. Octane didn't get high untill the 50s for street gas.

 

To get more compression from this engine would require 2 things. First would be domed pistons because the head has been shaved several times already and secondly, deeper pockets to buy the custom pistons. We tried different settings for the distributor but weren't happy with the results.