How much ethanol is too much

Katamarino

Katamarino

Pattern Altitude
Joined
Dec 14, 2011
Messages
2,099
Location
YPJT
Display Name
Display name:
Katamarino
Say you find yourself on an island, in an aircraft that can burn mogas. You have 80 gallons on board, but you need another 80 gallons to get to your destination and the only high octane mogas available has 5% ethanol.

Knowing that nothing is ever 100% certain - would running that diluted mogas through a C182 as a one-off concern you?
 
If the choice was use the mix and possibly have a problem vs stay on the island and certainly die... no contest.

If the choice was use the mix and possibly have a problem vs waiting for some other means of getting off the island...
 
Moderate to high concerns.

I took a class on fuel and lubricant chemistry in college. One of the lab activities was to test different rubbers in various solvents, and it was amazing how quick some of them would swell to more than double their size, or start falling apart.
I have no idea what kind of rubber hoses and o-rings are in your plane, but it's a good bet that there isn't any ethanol compatibility testing data on them.
Probably not a good thing to become a materials science test pilot over water.

I'd say you should look at having some approved fuel shipped over there. Maybe GAMI cand send you a couple drums of 100UL?
 
Any amount is too much IMO.

I think I would test the gas first to see what the % is? I never heard of 5% ethanol but who knows?
I am betting it is more than 5%?
I would hate to put any ethanol in a aluminum fuel system. Would it hurt just one time and you burn it out within a day or so I would probably do it?
But I would want to run it out within 24-48 hrs.
Also check that the gas is bright and clear and not cloudy. If it is cloudy then no way I would use it.
Maybe find another island to stop at? Probably not...
 
What does your STC say? The Airplane Flight Manual Supplement typically says 1% or less.
 
I run E-10 all the time, but I don't have "aircraft quality" fuel lines etc.
A buddy had a Kitfox that he "built the right way" - lost power on takeoff because his fuel lines had swelled nearly shut. But that took a while (don't know how long).

Got factory original stuff or has your fuel system been upgraded with some of the more modern materials?
 
The big problem in aircraft is that the ethanol absorbs water. But the amount it can hold varies a lot with temperature. So when you climb and the fuel gets cold, the water comes out of solution with the ethanol. If cold enough, it makes ice crystals that clog the fuel system.
 
Pinecone said:
The big problem in aircraft is that the ethanol absorbs water. But the amount it can hold varies a lot with temperature. So when you climb and the fuel gets cold, the water comes out of solution with the ethanol. If cold enough, it makes ice crystals that clog the fuel system.
Click to expand...
I'm assuming the plane is in a warm climate, and wouldn't worry about ice. The previously mentioned issues would give me more than just pause. It would give me ground stop.
 
If the natives are after you.....you have to go with what ya got....be ready to swim and fight off the sharks. ;)
 
How did I get my STC for the Cub to use auto gas? The Cub had rubber fuel lines and rubber gaskets and maybe an aluminum fuel tank (not sure about the tank).
 
dbahn said:
How did I get my STC for the Cub to use auto gas? The Cub had rubber fuel lines and rubber gaskets and maybe an aluminum fuel tank (not sure about the tank).
Click to expand...
I'm sure the STC requires non-ethanol fuel.

Pinecone said:
The big problem in aircraft is that the ethanol absorbs water. But the amount it can hold varies a lot with temperature. So when you climb and the fuel gets cold, the water comes out of solution with the ethanol. If cold enough, it makes ice crystals that clog the fuel system.
Click to expand...
Never been a problem for me, and I've been running E-10 for years. And, I have a hangar that literally drips from the rafters in the winter and floods in the summer. There are times you could skate in there. Really.
 
dbahn said:
How did I get my STC for the Cub to use auto gas? The Cub had rubber fuel lines and rubber gaskets and maybe an aluminum fuel tank (not sure about the tank).
Click to expand...
Were you running 10% ethanol fuel? :eek:
 
If that extra 80 gallons was in a ferry tank and a ferry system and I knew that I could run it out or clean it completely, with only a short run of incompatible airplane components in contact with it, I’d run it. Then inspect and/or replace seals and stuff so I could trust the entire system again.
 
Hate to burst everyone's bubble (not really, you'all just wrong sometimes).

What if I told you the FAA ran a Cessna 152 and an IO-540 on 100% ethanol and did nothing to airplane except a minor mixture adjustment?

The engine made MORE HP, and they could not get it to detonate.

The only thing stopping 100% ethanol is the petroleum industry and old wives tales. Rubber is not the problem. In 13 YEARS the 100% ethanol 152 never had a fuel related issue.
 
Pinecone said:
The big problem in aircraft is that the ethanol absorbs water. But the amount it can hold varies a lot with temperature. So when you climb and the fuel gets cold, the water comes out of solution with the ethanol. If cold enough, it makes ice crystals that clog the fuel system.
Click to expand...
NOPE.
 
Gary Ward said:
Any amount is too much IMO.

I think I would test the gas first to see what the % is? I never heard of 5% ethanol but who knows?
I am betting it is more than 5%?
I would hate to put any ethanol in a aluminum fuel system. Would it hurt just one time and you burn it out within a day or so I would probably do it?
But I would want to run it out within 24-48 hrs.
Also check that the gas is bright and clear and not cloudy. If it is cloudy then no way I would use it.
Maybe find another island to stop at? Probably not...
Click to expand...
How about any number from 1% to 100%? Everything you posted has been disproven in the mid 90's by Baylor University in a 13 years long study that that FAA buried.
 
Salty said:
Isn’t there a way to remove a lot of the ethanol by adding water, churning it up, letting it settle and then draining it out? Or did I dream that up?
Click to expand...
freeze it....and then filter the ice out?
 
Salty said:
Isn’t there a way to remove a lot of the ethanol by adding water, churning it up, letting it settle and then draining it out? Or did I dream that up?
Click to expand...
Ethanol is the octane booster. Remove it and your 91 mogas becomes something less. How much less? Don't know.
 
I've got an Ercoupe. I'm not flying to a remote island in the first place. LOL

If I could hold 80 gallons, that would give me a range of 1500 miles with a 100 mile reserve.
 
Sorry, pfarber, but I'll have to give you a [citation needed] on your statements. Some good research papers seem to contradict your statements (one is attached and a relevant part quoted below), but feel free to include documentation that supports your point of view. Also, nobody talks about 100% ethanol, but a blend of multiple molecules, where the sum is more than the individual parts.

One of the more dramatic changes in gasoline chemistry occurred with the addition of ethanol. The polar nature of ethanol increased the solubility of gasoline with some fuel system elastomers causing unacceptably high levels of swelling. Elastomers that have been shown to be susceptible to high swell with ethanol-blended gasoline include acrylonitrile butadiene rubbers (NBRs), styrene butadiene rubber (SBR), neoprene, and polyurethane.
Click to expand...

pfarber said:
Hate to burst everyone's bubble (not really, you'all just wrong sometimes).

What if I told you the FAA ran a Cessna 152 and an IO-540 on 100% ethanol and did nothing to airplane except a minor mixture adjustment?

The engine made MORE HP, and they could not get it to detonate.

The only thing stopping 100% ethanol is the petroleum industry and old wives tales. Rubber is not the problem. In 13 YEARS the 100% ethanol 152 never had a fuel related issue.
Click to expand...

pfarber said:
NOPE.
Click to expand...

pfarber said:
How about any number from 1% to 100%? Everything you posted has been disproven in the mid 90's by Baylor University in a 13 years long study that that FAA buried.
Click to expand...
 
Salty said:
Isn’t there a way to remove a lot of the ethanol by adding water, churning it up, letting it settle and then draining it out? Or did I dream that up?
Click to expand...
Yes, just like that. Mix/churn the corn liquor gas with fresh water and let it settle for as long as possible. Either drain off the water from the bottom or pour off the gas from the top. Mix with equal parts of your avgas and you should be good to go.
 
Checkout_my_Six said:
Were you running 10% ethanol fuel? :eek:
Click to expand...
Aha! No, I wasn't. My bad.

The STC is for autofuel, but non-ethanol only. We have that in abundant supply in Vermont, although it's more expensive than high octane auto gas. Mechanics have recommended that it be mixed with Avgas periodically for the beneficial effect of lead, which the old engines were designed around.
 
My hangarmate's Cessna 140 at KSSQ only purchased fuel from area FBOs. He had a substantial engine stumble on take off at Duluth' Sky Harbor airport :)oops:) which was found later to be elastomer fuel line related. I tested a sample of his fuel using the water-added method and found it contained about 5% ethanol. Calls to other FBOs in the area found a similar 5% water for supposedly "aviation grade" MoGas. The area fuel supplier had some months earlier apparently added ordinary E10 MoGas to E0 on a load.

Others at KSSQ happened to mostly use E0 from a marine based source. I never showed any water for my 172M kept at KSSQ. But I checked every load for negative ethanol thereafter.

I suspect there is a time-of-soaking requirement for fuel line swellings, but it probably is a few days at least.
 
The suggested aircraft is a C 182. They burn about 12 GPH at cruise. It will take 13 hours to burn all the mixed fuel in the tanks. Take off immediately, and you you get off the bad island, land at the good island, and purge the system at the airport. Fresh, good gas, and the deterioration is over. The key is that the time will be short for the deterioration. Max exposure, 13 hours.
 
Pinecone said:
The big problem in aircraft is that the ethanol absorbs water. But the amount it can hold varies a lot with temperature. So when you climb and the fuel gets cold, the water comes out of solution with the ethanol....
Click to expand...
I had a problem like that on the ground. I was renting a Rotax-powered plane whose owner was putting mogas in it, and the water separated out to the degree that the engine wouldn't start!
 
geezer said:
The suggested aircraft is a C 182. They burn about 12 GPH at cruise. It will take 13 hours to burn all the mixed fuel in the tanks. Take off immediately, and you you get off the bad island, land at the good island, and purge the system at the airport. Fresh, good gas, and the deterioration is over. The key is that the time will be short for the deterioration. Max exposure, 13 hours.
Click to expand...
The deterioration may not be reversible.

Many years ago I was the shop foreman in a heavy-duty brake component remanufacturing plant. Most of it was air brake related, but we did do the hydraulic boosters for medium-duty trucks as well. Some of that business was rebuilding boosters in systems that had been topped-up with motor oil where DOT3 fluid was not available. The rubber components in the master cylinder, booster and wheel cylinders or calipers are not compatible with petroleum oils, and they swell up as they absorb the oil. The damage is not reversible; the whole system has to be rebuilt.

The old Bendix/Stromberg aircraft carburetors used a steel float valve needle with a rubber tip. That tiny tip would swell if any ethanol got to it, and the swelling shuts off the incoming fuel and the engine quits. There have been accidents.
 
AV8R_87 said:
I took a class on fuel and lubricant chemistry in college. One of the lab activities was to test different rubbers in various solvents, and it was amazing how quick some of them would swell to more than double their size, or start falling apart.
Click to expand...
Never use solvents as a sexual lubricant.
 
We have not considered the penalty for staying on the island with the bad gas and cannibals'.

I am assuming that it is a little like the crew on the ISS, and the choice is either leave now with the gas available, or stuck for a long time. Cost of repair not an issue, parts available at the destination. Will the plane engine produce power for 13 hours?

And for the point of view of the younger guys here, the only gal on the island is Ginger.
 
You must log in or register to reply here.
Back
Top