Serious ethanol corrosion problems

Here in UK I understand that only 5% ethanol is added to standard unleaded at the moment although this is soon to rise to 10%.
I hadn’t really taken much notice of what some people had said about the possible consequences, but now wish that I had!
The picture below shows what is left of the brass filter in one of my Mk9 fuel tanks. It was ok 3 years ago when both tanks were drained in order for me to recondition the fuel pumps. The picture also shows the brass petrol filter. Notice the the petrol in the glass jar which has turned green.
I did have used the car for the last 3 years but not very much, but it isn’t as if if was filled up 3 years ago and not used at all.
I will be finding out soon what other damage has occured. I am concerned about the copper fuel lines, the brass floats and jets in the carbs, and the linings of the fuel tanks.
I have the head off at the moment in order to attend to a bent valve which occurred on startup after the winter hibernation. I’m blaming that on unleaded fuel as well, because the valves were all gummed up.
Anybody else had this problem.?
What’s the best thing to flush the tanks and fuel lines out with.?

I was thinking if using Car Plan engine degreaser.


I avoid E10 in my vehicles, unless they are designed for it…or ocassionaly 50/50 max in a tank…to help absorb & flush out water and other contaminants in the tank (water dissolves in ethanol)

It never should sit in a tank for a long time, or separation can occur

I am not a chemist, but wonder if some ethanol undergoes a change to methanol under certain conditions?

methanol is quite corrosive

We can get ethanol free fuel here, which is what I use, and I never use ethanol fuel in small engines such as chainsaw or mower

I have not tried but wonder what happens if brass parts are left in a glass jar of E10 and observed

I use BG44k religiously in all of my engines that sit over the winter upon spring wake up. This stuff removes a lot of gum and tarnish. It is my understanding that Jaguar engines have hardened valve seats and unleaded fuel has NO effect on them.

THe BG44k can be actually felt working in my wife’s little Honda 50 scotter as it starts giong faster and faster when the juice hits the carb.

I have also used “seafoam” and “Marvel Mystery Oil” with great results.

Hopefully they are available in your area.


I use 100LL/avgas in all my old cars, Mk2, E type, etc… It does not go bad like ethanol in a month or so. Best for the older cars that were designed to have some lead for lubricant. And made to sit for long shelf life with no issues. I have had two older cars/without catalytic convertors of course, lead ruins them instantly where they have their fuel lines eaten through with enthanol gas. Just not good for many parts on vintage cars.


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We have about four different grades in Australia. The E10 is 10% ethanol and up to 94 octane. Then three grades of “pure” petrol: 91, 95 and 98. I run only 95 and 98. Have seen examples of the pictured damage amongst club members’ cars. I believe it can also attack jet diaphragms. Paul

Well I remember a time when people said ethanol was a good thing.
If you do not run the gas through and burn it out with two weeks tops, in old cars with an open system.
It will turn to sugar water…eating up everything alive.
My old cars are running vr racing fuel 5 gallons at a time.
The additives almost work but start clogging up filters as people think 75 bottles of gas additive hold back the effect…
It doesn’t. The rubber hoses should all be upgraded to fuel injection or they will collapse within a couple of years.
Notice a lot more collector fires these days?
The other way is convert to electric, but that’s another kettle of fish!
TEST…One drop of ethanol fuel , just one drop on cement floor, then 1 drop of vr racing fuel
That’s all you need to do, the vr evaporates , odorless and no residue,ethanol leaves a stain, stinks and never goes away.

Hi Wardell, sorry to see the troubles shown in your pictures. Regardless of cause, you’ve got a mess there. Good luck on sorting back to pleasant running.

Here are a few thoughts on ethanol-laced fuel. I’ve been running standard lowest octane gasoline in California for nearly 20 years in my 1950 Mark V. The car has lived its entire life in California and so has been on unleaded fuel with ethanol a very long time.

My couple of decades with the car has averaged about 1,000 miles per year, which means I buy about 4 tanks of gas a year. The car regularly sits without running for one month a year and otherwise gets driven about once a week or less now. It used to be my daily driver but I don’t drive every day these days (bike to work) and have some other cars as well. I’ve never seen any ill effects from ethanol on the car. No green deposits or green fuel, the brass filters in the gas lines look as new, the copper lines are not leaking. The rubber hoses don’t show symptoms of problems other than age-related cracking.

Dyes are added to some fuels. I don’t know local practices in your area but some diesel fuels are sold with green dyes and some parts of the world put green dye in some levels of octane gasoline. And gas that is a few years old can have green color along with sludge. And where there is sludge in the fuel, there may also be concern for sludge in the oil, particularly of concern in places with small clearances such as valve guides.

Good luck on cleaning the fuel and oil lines and passages and arriving back to a great running engine.

I’ve only drained one tank so far as storing several gallons of waste petrol is a bit of a problem.
I’ll take a look at the other tank later this week, if that’s the same it’s a stale fuel problem, if it’s ok it’s water contamination probably from a blocked tank breather allowing water to backfeed into the tank.
I stripped the pumps 2 years ago, but they will need doing again, and will renew everything in the fuel line.
People need to check the colour of the fuel in the glass bowl fuel filter. It’s it’s gone green it means the brass filters are disintegrating and immediate action is needed.
I will be running a few bench tests on this type of petrol and it’s effects on brass, copper and aluminium alloys over the coming months and will report back my findings.
Thanks to all who replied to my post.

Good luck, Plated tanks, lines and braided stainless are the only way.
Fuel injection hose and your set, ANY old part no matter how small will contaminate everything.
Its a cancer.
Roger could have been saved for 2 reasons…
climate is stable, no snow, 30 to 80 degree changes, plus he drove his car on an almost weekly basis.
Farm areas have zero ethanol gas pumps as well in many parts of the US.
If 15 % gets approved , the old cars are done for unless you drive them or put in racing fuel.

With 44 years of unleaded gasoline in California, and now Oregon, and running 5 vintage British cars, two Morris Minors, one Austin 1300, one MGTD and one Jaguar 3.8S I have had no ill effects with unleaded fuel. Ten percent ethanol fuel has been the standard pump gasoline for, IIRC 15 years, and again I have had no ill effects. The cars sometimes sit for 4-6 weeks unused but most are used 15-40 miles or more a month. Octane choices are dependent on the car. MGTD the lowest (87) and the Jaguar 91. I have tried the “pure” gas from time to time and notice no difference in operation.

I’ve checked the other tank today and it’s the same story. When I removed the drain plug nothing came out and I had to rod it to get through the green sludge.
I then turned my attention to the carburetors and found that all the brass was just starting to be affected, although no permanent damage as yet.
The floats were discoloured and there was some deposits on the jets which slide in the guide tubes making them stick. The needle valves were no longer a shiny brass colour having turned a dull brown. The aluminium appeared undamaged.
God knows what the fuel pumps will be like!

All ditto, here in Colorado: all I’ve ever done is to run Sta-Bil thru the system, when stored for the winter months, in my small-engined lawn equipment, and the (just about as crudely-carbureted Jag and Rover.

Zero issues.

Guys its not the unleaded fuel…Its the Ethanol in the fuel.
Just put a couple of ounces in a glass jar, one with ethanol and one without.
Leave it on the shelf. You will be surprised.
The killer is it attacks all the diaphrams and seals and on old copper floats it eats right through it.
JOE CURTO has all new resistant rubber parts which does not dissolve.
ALL FUEL INJECTED cars from the early 2000’s have now switched to GREEN o rings as well.
Its a real issue.

Here is a link to corrosion studies of ethanol-gasoline fuels where the concentrations of ethanol are much higher than E10.

My impression is that corrosion issues for E10 fuel, or lower, are about the same as gasoline without ethanol. Effects due to ethanol are more important for fuels with 50% ethanol or higher. The water in the fuel system can be a contributor to corrosion, ethanol present or not. Tanks which breathe in fresh air via temperature swings can pull humidity into a tank. Presumably a low fuel level in tank will allow more breathing per day. Sludge buildup and water may present corrosion and blockage issues whether ethanol is present or not.

It may be that changing some of the materials can reduce some corrosion problems for cars where fuel sits unused for many months in the tank. I use a tank about once every three months and have not observed problems in my usage either from ethanol or unleaded considerations. I use no aftermarket additives, just standard pump unleaded, ethanol/gasoline straight out of the California pumps. One should still be mindful of sludge or corrosion possibilities (including brake systems) for cars without much usage.

From American Chemical Society listing:
Study of Corrosion of Metallic Materials in Ethanol-Gasoline Blends: Application of Electrochemical Methods, Energy Fuels 2017, 31, 10, 10880-10889

Google removing alcohol from gasoline.

Its simple and I have been doing it for years on the motorcycles.

The new “stabilizers” in gas don’t help either.

Here’s what the petrol gauge sender units looked like. Coverd with a 1/16 inch of crystallised grey kak!
Petrol pumps tomorrow !

I agree with Roger. I also live in Southern California where I’ve owned my 1967 Mark 2 for thirty years. I used 91 octane premium unleaded fuel in the car during that time and usually drive it once a week. I’ve encountered no problems with gas tank, fuel pump, fuel hoses or carburetors during that time.

Yes it is a problem if the car is allowed to stand unused.

You are in the UK and you need a UK solution, rather than the knowledge and comfort that others abroad haven’t had your misfortune.

The problem is that if the ethanol containing petrol is not used up promptly, it absorbs water from the surroundings and rust formation is promoted. In addition to that, if it stands unused long enough, the petrol starts to separate out and this is the grey jelly sludge you see.

Ethanol also attacks some rubber compounds and this can leave gaskets and O-rings compromised. Since it is a relatively new addition to petrol in the UK, the rubber parts in the fuel supply chain
for vehicles as old old as yours will not have taken this into consideration until very recently.

The easiest advice is to use up the petrol before it goes off. One way to do that would be to disconnect the fuel pump and run the car dry. Then reconnect the pump but redirect the outlet to a jerry can and use it in your day to day car.

If you also have no catalytic converter worries, then your local airfield will have more suitable ethanol free fuel at about £2per litre.

kind regards

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Good advice. Another solution to the “gas sitting in the tank too long” problem would be to only fill the tank with enough gas to get you around for a couple weeks. Unless you’re going cruising, this will help keep fresh fuel in the tank.
I have the two tanks in my XJ12C and I switch from tank to tank regularly and only fill them with about 5 gallons of fuel. Seems to work.

Works in your high dry climate. If you’re in the higher humidity environs it will produce condensation in the tank. Filling with clear fuel for winter storage is common for our area.