Fuel in a "broken" airplane

[saracelica]

Not sure if I ever saw this come up so I figured I'd ask. Our club as an airplane that's been down for a bit (the fuel gauge doesn't read correctly - it is a Cessna after all) So it's offline (in maintenance) awaiting proper parts/diagnosis. How long can fuel just sit in an airplane without damaging anything? I don't think it has a rubber bladder or anything so it's just sitting in the wings. It gets moved by tractor in and out of the maintenance hangar. Was just wondering if you PoA'ers think I should suggest getting the fuel out of it and when we need to fly it out somewhere we put in "fresh" fuel.

 

[Tom-D]

Not sure if I ever saw this come up so I figured I'd ask. Our club as an airplane that's been down for a bit (the fuel gauge doesn't read correctly - it is a Cessna after all) So it's offline (in maintenance) awaiting proper parts/diagnosis. How long can fuel just sit in an airplane without damaging anything? I don't think it has a rubber bladder or anything so it's just sitting in the wings. It gets moved by tractor in and out of the maintenance hangar. Was just wondering if you PoA'ers think I should suggest getting the fuel out of it and when we need to fly it out somewhere we put in "fresh" fuel.

Auto fuel ? about a week.
100LL ? I've never seen it go bad.

 

[Ted]

Auto fuel ? about a week.

I've had many a vehicle sit over the winter, typically ends up being about a 4-month period. So long as it has a full tank of fuel before I put it away, it does fine. Where I see problems is when it sits for years on end.

100LL is designed specifically to have a virtually infinite shelf life, and without a doubt does better.

 

[Matthew]

There's a 172 hangar queen at one of my airports. It's been sitting for at least 5 years on flat tires, maybe even longer than that - no one can remember the last time it moved. The owner finally decided to sell it so the local A&P did what he could to see if the engine would even turn over. I think he just walked away when he found out it had been stored with auto-gas that whole time.

 

[Capt. Geoffrey Thorpe]

I just flew my ride yesterday for the first time this year. So, the 8 or so gallons of auto gas that were in it are at least 1 month old.

Fired right up. Flew just fine.

 

[saracelica]

Thanks everyone. I now learned something today!

 

[dmccormack]

An A&P who's been around assured me I could "freshen up" some MOGAS (non-alcoholic) that had been sitting 3 months with fresh gas.

Apparently it's true...

 

[Cap'n Jack]

Auto fuel ? about a week.
100LL ? I've never seen it go bad.

Auto fuel- I keep it over 6 months, seems Ok. 100 LL isbetter in that respect.

 

[denverpilot]

I wonder about mixed auto and 100LL.

 

[Tom-D]

There three main ingredients in auto fuel, 10% toluene, 10% Benzene, and 80% white gas stocks. those three ingredients each have a different specific gravity, benzene being the heaviest, it will settle to the bottom of the tank, toluene will separate to the center of the tank and of course the white gas stocks will be the top.

So start your engine and run it on benzene, It's ok with me.

even after the rest of the fuel has been shaken back into solution the oct rating won't be right, because you burned the benzene off the bottom first.

 

[Tom-D]

Auto fuel- I keep it over 6 months, seems Ok. 100 LL isbetter in that respect.

Is it in a open vented container like your aircraft tank.

it's all in the storage.

 

[Geico266]

I just flew my ride yesterday for the first time this year. So, the 8 or so gallons of auto gas that were in it are at least 1 month old.

Fired right up. Flew just fine.

Whoa! Please do not do that again. You are lucky! I helped picked up an ultralight out of a corn field when the owner took off with 6 month old gas in it. You could see "corn flakes" floating in the fuel.

I use auto fuel all the time, but you need to be very careful, and vigilant. Auto fuel looses 1-2 octane points every 30 days depending on the circumstances. 30 days is the limit for my aircraft without adding fresh fuel. Under certain circumstances old fuel can cause a layer of varnish "stuff" to form in the tank and break up and clog the filter or carb needle seat. Looks like corn flakes floating around.

Next time add 10 gallons of fresh fuel or better yet 100ll. This will disolve the "scum" or varnish layer.

 

[Geico266]

An A&P who's been around assured me I could "freshen up" some MOGAS (non-alcoholic) that had been sitting 3 months with fresh gas.

Apparently it's true...

Yes, and highly recommended.

 

[Geico266]

I wonder about mixed auto and 100LL.

Flying or storage with mixed fuel no problem. The 100ll acts like a stabilizer depending on the amount. 30% 100ll is a good mix point for storage for 3-4 months.

I mix it all the time going CC.. no issues.

 

[TangoWhiskey]

The fuel (if avgas) isn't a problem being stored in the plane.

In fact, it's probably beneficial. I'd worry more about bladders, gaskets and seals drying up if you left the tanks drained for an extended period of time.

 

[dell30rb]

old gas will also make your valves stick. My uncle trashed the pushrods and valve train on an old 460 V8 ford from old fuel.

 

[Tom-D]

I'd worry more about bladders, gaskets and seals drying up if you left the tanks drained for an extended period of time.

It's better to leave them empty than leave auto fuels in them for extended periods of time.

They set empty on the shelf for years and nothing dries out.

Soak them in Benzene and Toluene for extended periods and see what happens.

 

[TangoWhiskey]

It's better to leave them empty than leave auto fuels in them for extended periods of time.

They set empty on the shelf for years and nothing dries out.

Soak them in Benzene and Toluene for extended periods and see what happens.

I was speaking of AVGAS, not auto fuel. You quoted me, but not my first sentence, which specifically said Avgas.

 

[Tom-D]

I was speaking of AVGAS, not auto fuel. You quoted me, but not my first sentence, which specifically said Avgas.

Doesn't really matter, empty doesn't hurt.

 

[Cap'n Jack]

There three main ingredients in auto fuel, 10% toluene, 10% Benzene, and 80% white gas stocks. those three ingredients each have a different specific gravity, benzene being the heaviest, it will settle to the bottom of the tank, toluene will separate to the center of the tank and of course the white gas stocks will be the top.

So start your engine and run it on benzene, It's ok with me.

even after the rest of the fuel has been shaken back into solution the oct rating won't be right, because you burned the benzene off the bottom first.

Tom- your "chemistry" always amuses me. All of those compounds are completely miscible with each other and won't demix upon standing.

Your statement is like saying that the water and alcohol in a cheap vodka will separate over time based on specific gravity with the water being on the bottom after sitting on your counter for a week.

 

[Cap'n Jack]

Is it in a open vented container like your aircraft tank.

it's all in the storage.

Just kept in a lawn mower or snow blower over the off season. The tanks are vented.

 

[Tom-D]

Just kept in a lawn mower or snow blower over the off season. The tanks are vented.

What are talking a qt of fuel? Every time I leave fuel in my mower, I can't get it started until I change it. so I run it out, and add new fuel the next time I use it.

and we mow every month here.

 

[TangoWhiskey]

Doesn't really matter, empty doesn't hurt.

Good to know, thanks. So when they talk about rubber seals and things deteriorating, is that related to ENGINE and PROP components, and running those often to keep good oil moved over them? I can't think of many "rubber" components that would be in a fuel system with metal lines, other than maybe fuel bladders.

 

[Cap'n Jack]

What are talking a qt of fuel? Every time I leave fuel in my mower, I can't get it started until I change it. so I run it out, and add new fuel the next time I use it.

and we mow every month here.

Quart to 5 gallons, depending on the mower/blower or storage container. Never had a problem. It all stays in the garage that ranges from icy cold to >100° F.

Did you know that toluene and benzene have nearly the same specific gravity? Both pretty close to 0.87 at 25°C.

 

[denverpilot]

Auto fuel looses 1-2 octane points every 30 days depending on the circumstances. 30 days is the limit for my aircraft without adding fresh fuel.

But the fresh fuel doesn't put the lost octane points back. So do you drain and get rid of it completely if it's 30 days old?

Do automotive collectors drain all fuel from cars that drive only in summer?

Just curious.

 

[jesse]

Quart to 5 gallons, depending on the mower/blower or storage container. Never had a problem. It all stays in the garage that ranges from icy cold to >100° F.

Did you know that toluene and benzene have nearly the same specific gravity? Both pretty close to 0.87 at 25°C.

Mowers and snow blowers are quite tolerant of bad gas but it's still not that good for them.

Take a four cylinder jap bike that has 4 carbs and leave mogas in it for a year and you're looking at a very expensive repair.

 

[Piloto]

A good indication of the fuel age is the smell. If it no longer smell like new fuel discard it.

José

 

[N801BH]

Every one of my gas powered pieces of equipment that does not have a catalytic converter gets 100LL when I park them for the season...
1- Better then stabil,,

2- easier to get and,

3- it smells better too when they run...


Ben.

 

[DaleB]

Hmm. Every one of mine (mower, weed whacker, leaf blower, snow blower, '55 Vespa scooter, Harley) just gets a "regular old" gas, 10% ethanol and all. No Sta-bil, no Marvel mystery oil, no chicken blood or incantations. Have been doing that for a couple of decades now, with zero issues. They all start right up in the spring (fall for the snow blower), too. Usually on the first pull/kick/crank. Guess I must be doing it all wrong.

None of those are airplanes, though. Don't have one of those yet, but when I do I can't imagine gas sitting in it for very long.

 

[Tom-D]

Hmm. Every one of mine (mower, weed whacker, leaf blower, snow blower, '55 Vespa scooter, Harley) just gets a "regular old" gas, 10% ethanol and all. No Sta-bil, no Marvel mystery oil, no chicken blood or incantations. Have been doing that for a couple of decades now, with zero issues. They all start right up in the spring (fall for the snow blower), too. Usually on the first pull/kick/crank. Guess I must be doing it all wrong.

None of those are airplanes, though. Don't have one of those yet, but when I do I can't imagine gas sitting in it for very long.

and they all have a compression ratio of what 6:1 ?

 

[Tom-D]

A good indication of the fuel age is the smell. If it no longer smell like new fuel discard it.

José

We have a winner..

 

[Tom-D]

Good to know, thanks. So when they talk about rubber seals and things deteriorating, is that related to ENGINE and PROP components, and running those often to keep good oil moved over them? I can't think of many "rubber" components that would be in a fuel system with metal lines, other than maybe fuel bladders.

hopefully the prop never gets any fuel in it,

The rubber used way back then was real rubber, and when soaked in Toluene and benzene, it will dissolve the resins in the rubber compounds, but as long as the rubber remains wet it will remain soft. when it is allowed to dry out the rubber turns to black chips, cracks very easy.
There are tank bags that are made for auto fuel, but they are not a rubber compound.

part materials change, old wives tales don't.

 

[Richard]

part materials change, old wives tales don't.

My new sig line.

 

[Ted]

Doesn't really matter, empty doesn't hurt.

I know a number of A&Ps and aircraft owners who will disagree with you on this point, and say that leaving the bladders empty does contribute to them drying out faster and leaking.

Whether you're right or they're right, I don't know. But I always keep the Aztec tanks full for that reason.

Take a four cylinder jap bike that has 4 carbs and leave mogas in it for a year and you're looking at a very expensive repair.

I am, perhaps, the only person who's never had problems with carburetors on 4-cylinder Jap bikes, and I've owned plenty of them. I just make sure that I top the things off before winter, and then in the spring when it's time to start them up, no problems.

The one time I had a problem was when I tried to start my Bandit 1200 in December, when it was about 10F out. The plugs, which were weak, ended up fouled up completely and I had to replace them before it would run. But again, no carbs.

Never used Stabil, either, and no problems. This is on a total of probably 15-20 vehicles I've owned that have sat over the winter at one point or another, mostly old motorcycles and cars.

 

[flyingron]

Avgas has additives because it's expected to sit around a bit more than car gas. I'd not worry about it. I've fired up planes that have sat for prolonged times without a problem.
Your engine has bigger issues with the inactivity than avgas.

 

[Capt. Geoffrey Thorpe]

Whoa! Please do not do that again. You are lucky! I helped picked up an ultralight out of a corn field when the owner took off with 6 month old gas in it. You could see "corn flakes" floating in the fuel.

I use auto fuel all the time, but you need to be very careful, and vigilant. Auto fuel looses 1-2 octane points every 30 days depending on the circumstances. 30 days is the limit for my aircraft without adding fresh fuel. Under certain circumstances old fuel can cause a layer of varnish "stuff" to form in the tank and break up and clog the filter or carb needle seat. Looks like corn flakes floating around.

Next time add 10 gallons of fresh fuel or better yet 100ll. This will disolve the "scum" or varnish layer.

I'm very familiar with varnish having owned old boats that had set for years at some point in their lives.

If he had "corn flakes" he did more than just let it sit for 6 months on one occasion. I assume this was a two stroke? Likely he mixed in two incompatible two stroke oils.

I typically add gas regularly. But 100LL is a fuel of last resort - gearboxes are expensive and lead does not lead to longevity.

 

[Cap'n Jack]

hopefully the prop never gets any fuel in it,

The rubber used way back then was real rubber, and when soaked in Toluene and benzene, it will dissolve the resins in the rubber compounds, but as long as the rubber remains wet it will remain soft. when it is allowed to dry out the rubber turns to black chips, cracks very easy.
There are tank bags that are made for auto fuel, but they are not a rubber compound.

part materials change, old wives tales don't.

It's better to leave them empty than leave auto fuels in them for extended periods of time.

They set empty on the shelf for years and nothing dries out.

Soak them in Benzene and Toluene for extended periods and see what happens.

Tom- You don't know avgas has up to 10% toluene in it?
http://www.phillips66aviation.com/pdfs/AvGas MSDS.pdf

 

[Geico266]

I'm very familiar with varnish having owned old boats that had set for years at some point in their lives.

If he had "corn flakes" he did more than just let it sit for 6 months on one occasion. I assume this was a two stroke? Likely he mixed in two incompatible two stroke oils.

I typically add gas regularly. But 100LL is a fuel of last resort - gearboxes are expensive and lead does not lead to longevity.

Yes, it was a two stroker.


I know you are experienced and are careful, just be vigulant. Bad fuel can ruin a good day.

 

[Capt. Geoffrey Thorpe]

Yes, it was a two stroker.


I know you are experienced and are careful, just be vigulant. Bad fuel can ruin a good day.

Friends don't let friends fly behind two strokes.

A buddy was running pump fuel with ethanol and had an engine failure on takeoff when his aircraft grade fuel lines swelled shut.

OOPS.

(Amphibian on a long lake. Coasted to a stop with no problem.)

I use the SAE (automotive) spec stuff myself. One less thing to worry about.

 

[DaleB]

and they all have a compression ratio of what 6:1 ?

Depends. Not sure about the 2-strokes, Tecumseh and Briggs. The Vespa runs around 8 or 8.5:1, and the Harley is pushing 9.5 or so. Since you asked.