Warning, Fuel phase separation !!!

[driftin jo]

Ethanol blended fuels (E5,E10 etc). Phases separation !

About a week ago a helped a friend of mine empty his fuel tank as he had to remove it, not an Audi but that isn't relevant, he asked me if I wanted the gallon and a half of fuel as he was going to flush the tank out to get any crap out of it.
I said I would have it for cleaning things as I didn't want to put it in the S2 and my other car is a TDI. The only container we had to pour the fuel into was an old brewing bin (big plastic bucket with a snap on lid).

After we poured the fuel into it I noticed that there was a line that looked as if the fuel had separated.
After looking closer there was indeed a line of separation !

This got me thinking, I asked had he ever put diesel in the car by mistake and in five years of ownership he had not so that ruled that one out, I asked him where he bought petrol and he said mainly the shell garage but lots of other garages as well.

I had a look online and it turns out that this is quite a concern in the US already.

The problem is that E5 and E10 petrol is now widely sold and as far as I'm aware in the UK they are not even required to tell you that the petrol you are putting in your tank has ethanol in it.

I'm almost certain that v power and tesco 99 ron are E5 (with additives ) and I'm guessing a lot of other petrol may also be E5 or even E10 !

I know a lot of people are going to think that this is a good thing as this gives us a nice high octane number that our cars like, but here is the catch. Ethanol is Hygroscopic ( attracts and hold water)
and if you get even a small amount of water absorbed by the ethanol the petrol ethanol mix Phase separates as the ethanol part of the mix becomes heavier.

This happening in your petrol tank is quite likely as you seldom let your tank run very low and the ethanol is now at the bottom of your tank just waiting for you to go into the reserve and then your car goes from running petrol to running almost pure ethanol in a matter of minutes.

The other concern is that this can happen at the petrol station in the underground tanks and if it has happened and you happen to fill up just before the tank runs out you could be filling up with ethanol with no petrol in it !

Appernly the petrol companies are on to this and have installed an alcohol monitors that the fuel has to pass through as it comes up from there tank to make sure that concentration is correct but I'm not sure if all stations have this if any in the UK.

So if you run down into the reserve and you haven't done for a good wile and you car suddenly starts to run like a bag of crap this may be the reason.

This link is interesting as it shows that the alcohol monitors that they have installed
at petrol stations don't prevent phase separation in your tank !

http://www.youtube.com/watch?v=rO3x5o0W7-M

[Error404]

This is worrying, I'm sure all fuel now by law in the EU has to have at least 5% ethanol content.
Was this the problem Tesco (or was is ASDA?) had a while back where they had to compensate lots of drivers for damage resulting from fuel quality issues?


Is this another good reason to dump the carbon canister? Surely the evapouration process will suck water vapour back into the tank?

[andy10v]

And if it is seperated the remaing fuel minus ethanol will no longer be the octane rating it was sold as?

(Stops fillling car up on misty/rainy days , oh wait, I live in scotland )

[ian4455]

In my Town last year a supermarket petrol station caused hundereds of cars to breakdown - lambda sensors, would this have been the cause ?

[Thuppu]

http://www.cim-tek.com/pdfs/Treatise_on_Phase_Separation.pdf

[driftin jo]

In my Town last year a supermarket petrol station caused hundereds of cars to breakdown - lambda sensors, would this have been the cause ?

probably

[driftin jo]

This is worrying, I'm sure all fuel now by law in the EU has to have at least 5% ethanol content.
Was this the problem Tesco (or was is ASDA?) had a while back where they had to compensate lots of drivers for damage resulting from fuel quality issues?


Is this another good reason to dump the carbon canister? Surely the evapouration process will suck water vapour back into the tank?

I hadn't though of that, how does the evap work ? does it just remove vapour until the pressure is in equal or is there a vent /one way valve that can let air in ?
Even if this isn't a concern it has been shown that it can pass the petrol stations alcohol test that essentially checks for separation then when it gets in your cold tank 'bingo' it separates.
I forgot to mention in my last post that I tested the separated fuel from the tank and the stuff from the bottom burned clean like you would expect alcohol to do the stuff of the top just like petrol, I did this just to make sure it wasn't just water he had in his tank, proof enough for me.

The only thing I can conclude is it would be better to run your tank nice and low before refilling
but that is not good either in my book and it doesn't help if it separating the second you fill up at the pump in cold weather anyway !

[Error404]

the fact the pump draws from the bottom of the tank though, surely once it's separated, you're sucking down the heavier element anyway

[driftin jo]

the fact the pump draws from the bottom of the tank though, surely once it's separated, you're sucking down the heavier element anyway

Yes It is , I suppose I depends how deep the separation layer is, (obviously this will get deeper over time) does anybody know what depth of fuel is in the tank when you run out ?
It would be good to put a tap at the very bottom of your tank and run it out of fuel normally then open the tap to get what the pump can't and see what comes out.

[PeteRR]

Not only separation and the acids created by this process, but this crap can also eat the rubber seals and hoses in older fuel systems. As well as degrade brass, copper, tin, zinc, etc, etc. It also ruins the glassfibre and plastic fuel tanks on some bikes and boats (potentially lethal!) and dissolves most tank linings, chucking the resulting goo into the fuel system.

And levels of Ethanol are set to increase in the future. As someone that runs a classic car, the quattro and a bike on carbs this is a major cause for concern.

It beggars belief that someone thought that it was a good idea to contaminate our fuel with this stuff with the usual misguided 'environmental' agenda that doesn't even stack up!

[EspenW]

The lower the ethanol content, the lower the percentage needed for phase separation. When testing the ethanol content in our local E85, I had to add approx 50% water to the mix before phase separation would occur.
Ethanol can be a concern for cars built before approx. 1985, but most cars built after that date will tolerate it just fine. My Golf from 1986 has been running E85 since 2006 without issues whatsoever. It enables it to run a 11:1 CR on the 8v engine.
As a performance fuel, especially for a turbo car, ethanol is on a completely different level, with instant 10-25% gain all over the rev range (once proper measures are made for fueling).
To illustrate the difference, imagine a fuel with the following properties vs. petrol:
10-25% less torque and power at the same boost/timing
50-100 degrees higher EGT
Significantly slower spool
Much more carbon buildup in combustion chamber and on valves
30% better fuel mileage.
Better cold start properties

If someone introduced a fuel with such properties vs. petrol, it probably wouldn't attract many customers, especially not performance oriented ones. However, that is how rotten pump fuel stacks up against E85. Ethanol has its disadvantages, but overall, it is a much better fuel for turbo cars in particular.

[mcandmar]

I have heard this argument before so interesting to hear about your finding. I run my S2 on E5 fuel as its the only substitute for true 98 octane fuel we have here.

Question is once the fuel has separated does it stay like that or will it return to normal when heated and sloshed about in the tank?

[driftin jo]

The lower the ethanol content, the lower the percentage needed for phase separation. When testing the ethanol content in our local E85, I had to add approx 50% water to the mix before phase separation would occur.
Ethanol can be a concern for cars built before approx. 1985, but most cars built after that date will tolerate it just fine. My Golf from 1986 has been running E85 since 2006 without issues whatsoever. It enables it to run a 11:1 CR on the 8v engine.
As a performance fuel, especially for a turbo car, ethanol is on a completely different level, with instant 10-25% gain all over the rev range (once proper measures are made for fueling).
To illustrate the difference, imagine a fuel with the following properties vs. petrol:
10-25% less torque and power at the same boost/timing
50-100 degrees higher EGT
Significantly slower spool
Much more carbon buildup in combustion chamber and on valves
30% better fuel mileage.
Better cold start properties

If someone introduced a fuel with such properties vs. petrol, it probably wouldn't attract many customers, especially not performance oriented ones. However, that is how rotten pump fuel stacks up against E85. Ethanol has its disadvantages, but overall, it is a much better fuel for turbo cars in particular.

It isn't really an issue for you as you are running E85 and as you say the alcohol can stand a lot of
water before it separates. Even if it did it's hardly going to matter if you are tuned for 85% alcohol.
The issue is that a normal petrol tuned car could end sucking up 90+ % ethanol and a normal car tuned for petrol is not going to like that at all.
Imagine you a giving it some in an S2 and you just get down low enough in the tank to start sucking up 90% alcohol that has separated , you would go very lean and possibly melt a piston.

[driftin jo]

I suppose the only solution is to re tune for E85 to ovoid the possible problems.