The Munster Vintage Motor Cycle & Car Club Ltd






Ethanol in petrol (by kind permission IVVCC)

John Larkin's personal summary.

RIGHT NOW: There is no definitive citable paper available yet that clarifies the problem of ethanol in petrol for old vehicles. What seems to be clear is that 5% ethanol in petrol has not proven to be a significant issue in old cars that are used regularly.  The problems so far encountered seem to be related to long periods of non-use where the ethanol separates from the petrol and absorbs water resulting in a corrosive mix lying at the bottom of the fuel tank often resulting in tank perforation and fuel leaks --- a serious fire risk. Starting up such vehicles can be problematical.  It seems that petrol with 10% or higher ethanol leads additionally to degradation of elastomer/rubber fuel lines (Ford and VW had huge problems with this in Brazil some decades ago).  Marine and aircraft manufacturers generally advise against ANY ethanol being used in their craft.  There seems to be a body of evidence growing that ethanol corrodes zinc, brass, copper, aluminium and lead in addition to denaturing elastomer/rubber components.  Ethanol vents off at altitude and can cause icing in carburettors. In April 2008 the German environmental minister cancelled a proposed 10% ethanol fuel scheme citing technical problems for older cars.  The majority of cars produced before 2000/2004 is not E10 compatible.

THE FUTURE: 5% ethanol in petrol (common now in Ireland) has not YET proven to be a major issue in older vehicles that are used regularly.  The German government considers 10% ethanol mix to be unsafe for older vehicles, and so have continued to permit petrol sales with much lower ethanol levels. The conservative position for old vehicles seems to be that ethanol is unsafe at levels over 5%.  There is a high probability that ethanol will reach 10% in petrol after 2013, although 5% ethanol may be simultaneously available alongside it for a time.   It seems certain that the minimum level of ethanol in petrol will be 10% from 2020, and that the actual level may be as high as 20%.  It is clear that many old vehicles will need to have fuel system components changed to materials that are not affected by ethanol.  Carburettors may need re-jetting, and adjustments may be required to ignition timing.

You can measure the amount of ethanol in your petrol like this:  On a tallish clear glass bottle make a permanent line about two inches from the bottom.  Fill with water to this line, and then fill the bottle to the top with petrol.  Put the lid back on tightly and shake the bottle well.   Leave it to stand until it settles fully.  Ethanol mixes with water and the two will separate out together as a single liquid phase at the bottom of the bottle.  If the level of this mixture is higher than the mark to which you filled the water then the fuel contains ethanol.  Super Grade petrol from Texaco/Chevron contains no ethanol, and this may be the case for other suppliers also.

Remember, ethanol as a fuel is of lower efficiency than petrol, and there is evidence that its use may be more polluting than the petrol it replaces.

Other articles and references can be found below.

Compatibility of materials with ethanol (added 11:00 24 March 2011)

Source: FBHVC website:




Not Recommended


Carbon steel with post-weld heat treatment of carbon steel piping and internal lining of carbon steel tanks

Zinc and galvanised materials

Stainless steel





Lead/tin coated steel


Aluminium (may be an issue for E100)


Buna-N (hoses & gaskets)

Buna-N (seals only)


Neoprene (seals only)


Urethane rubber

Neoprene (hoses & gaskets)

Acrylonitrile-butadiene hoses

Polysulfide rubber

Polybutene terephthalate







Polymers containing alcohol groups (such as alcohol based pipe dope)


Nylon 66

Fibreglass-reinforced plastic

Fibreglass-reinforced polyester and epoxy resins








Click here for the Irish legislation that mandated ethanol in petrol: Energy Act 2010

(added 11:15 23 March 2011 JL )


5% ethanol in petrol increases fuel consumption by 2%.  10% ethanol increases fuel consumption by 4% and 20% ethanol by 9%.   (Ethanol energy content is 26.8MJ/kg.  Petrol energy content is 44.4MJ/kg. Source: Wikipedia).  (JL added 17:19 22 March 2011.)


This is a list of manufacturers whose cars are E10 compatible.  It is clear that E10 compatibility did not really commence until the late 1990s, with many not achieving that status until the mid-2000s.  This seems to exclude all of our cars. Added by JL 14:24 22 March 2011.



Compatibility with E10



BMW Mini


Rolls Royce

2003 onwards

Mercedes Benz

2002 onwards

All fuel-injected vehicles not equipped with three-way catalysts.



Alfa Romeo

2005 onwards


2000 onwards, with several exceptions


1992 onwards except for Mondeo SCI CD 132 until 2006.


1992 onwards

Land Rover

1996 onwards


Information vague.


1998 onwards.


2000 onwards.


1997 onwards with exceptions.


1998 onwards with exceptions.


2000 onwards with exceptions.


1992 onwards with exceptions.


1999 onwards with exceptions.


Generally not suitable.


1996 onwards, except for S/V40 model with 1.8L engine.


Mid 1980s onwards.


2008 onwards


Information vague.


2000 onwards


2002 onwards


Information vague.


1991/1994 onwards


Information vague.


Added 13:37  22 March 2011

The following was sourced from the website of the Irish Aviation Authority at 13:34 on 22 March 2011:

7. Adverse effects of using MOGAS containing alcohol

7.1 - The probability of vapour lock increases when ethanol is mixed with fuel.

7.2 - Ethanol is hygroscopic in nature and therefore it will mix with water.   This can be in the form of water vapour from air or condensation from inside tanks or free water.  Very small amounts of water can be absorbed without significantly affecting combustion, at higher levels the mixture will not be combustible.  In addition, because this incombustible fuel is formed from a mixture of the ethanol in the fuel and the water it can have a large volume - so a small amount of water will result in a much larger amount of incombustible ethanol/water mix.  This can lead to false readings in the fuel tank sumps or exceed the volume of the sump altogether.

7.3 - Ethanol is an Octane booster and can be absorbed by water.  The mixing of fuel and water can effectively wash the ethanol out of the fuel resulting in a significant reduction to the remaining fuel's Octane rating.

7.4 - An engine will use more fuel as the percentage of added alcohol increases.  An approximate figure is that the engine must burn 3% more fuel to give the same power output if the fuel contains 10% ethanol.

7.5 - Ethanol mixed with water is somewhat corrosive and may attack parts of the fuel system. In long-term storage, Ethanol may oxidise with exposure to air.  This process produces a mild acid solution which can attack fuel system fittings.

7.6 - Long term exposure to ethanol damages some types of plastics (elastomers), therefore items such as flexible fuel lines are subject to increased deterioration.  Some of the elastomers used in old aircraft models and which are otherwise compatible with Avgas may deteriorate on contact with ethanol.

8. Carburettor Icing: Carburettor icing is more likely when using MOGAS because it has a higher volatility (and possibly a higher water content) than AVGAS.

 Wikipedia information added 11:12  22 March 2011:-  Fuel system problems.    See also: E85 in standard engines#Risks .    Fuels with more than 10% ethanol are not compatible with non E85-ready fuel system components and may cause corrosion of iron components.[193][194] Ethanol fuel can negatively affect electric fuel pumps by increasing internal wear,[194] cause undesirable spark generation,[195] and is not compatible with capacitance fuel level gauging indicators and may cause erroneous fuel quantity indications in vehicles that employ that system.[196] It is also not always compatible with marine craft, especially those that use fibreglass fuel tanks.[197][198] Ethanol is also not used in aircraft for these same reasons.   Using 100% ethanol fuel decreases fuel-economy by 15-30% over using 100% gasoline; this can be avoided using certain modifications that would, however, render the engine inoperable on regular gasoline without the addition of an adjustable ECU.[199] Tough materials are needed to accommodate a higher compression ratio to make an ethanol engine as efficient as it would be on gasoline; these would be similar to those used in diesel engines which typically run at a CR of 20:1,[200] vs. about 8-12:1 for gasoline engines.[201]   In April 2008 the German environmental minister cancelled a proposed 10% ethanol fuel scheme citing technical problems: too many older cars in Germany are unequipped to handle this fuel. Ethanol levels in fuel will remain at 5%.[202]

This article is reprinted courtesy of Zach Merrill of the FOOTHILLS BRITISH CAR CLUB ( and is dated February 2010

Living with a Tipsy Classic


Your LBC and Ethanol

In my youth, my father ran a wrecker service. As a result of my exposure to that sometimes-dreadful business, witnessing other people's hard-learned lessons convinced me that mixing alcohol and automobiles can lead to unfortunate consequences. That truism has never been more true than it is today. Until recently, it was only the operator who sometimes disastrously opted to imbibe. These days, our legislative officials have seen fit to force alcohol on our machinery as well.

It is very difficult to avoid being forced to be a consumer of 10% ethanol mixed with 90% gasoline. In ordinary operation in a modern vehicle, other than a slight degradation in fuel economy, the evil brew yields little to complain about. In vintage vehicles, small engines, and marine craft, however, it can be another matter entirely. Modern fuel injected vehicles with high-pressure fuel systems and feedback-loop fuel management can generally burn 10% ethanol and be content. The fuel system samples the O2 output in the exhaust, richens the mixture a sniff and goes on about its day. Use 10% ‘ethanol enhanced’ gasoline (hereafter referred to as E10) in a carburetted engine with no O2 feedback, and the scenario likely won't play out quite as well. Toss in the additional issue of an atmospherically-ventilated fuel system combined with infrequent use, and you have the making of a very unhappy experience. Even in the best of circumstances, a vintage carburetted engine running on E10 is compromised. If the fuel/air mixture had been optimized for gasoline, it will be a sniff lean on E10. True enough, the mixture can be recalibrated if someone knows how to do it and then actually follows through. Expect to lose about 7%(ish) fuel economy though and expect the engine to have some issues with hot weather driveability, but it will generally run more or less OK.

There are some real potential issues with attack of rubber polymers and there is a risk of crud being dislodged and causing clogging. Still, most old cars sorta-almost-nearly run OK most of the time on E10 if the engine is operated regularly and the fuel is not allowed to age more than a few weeks. Aging a really bad thing. I am reminded with each look in the mirror, but even I age well compared to E10.

Ethanol has a major affinity for moisture. Store E10 in a modern vehicle with a sealed (not atmospherically vented) fuel system, and it still only stays fresh about 12 weeks. Put E10 in your vintage classic with its vented fuel system, and within a mere month, the fuel is no longer fresh. Leave the fuel in the tank just a few months, and you are facing disaster. The alcohol absorbs moisture from the air. The fuel experiences phase change. The moisture laden alcohol separates from the gas and settles to the bottom. It becomes highly corrosive. As if that were not bad enough, the remaining gasoline has very poor octane and the whole miserable concoction has a terrible tendency toward oxidation. Good old-fashioned red Sta-bil helps retard the oxidation, but it does not help with the moisture absorption and the phase change issue. For emphasis, let me remind you this moisture absorption happens because the alcohol sucks the moisture right out of the air and this condition occurs readily if the fuel is contained in a vented tank and/or fuel bowl (as is the case with vintage cars, boats built prior to 1977, and most small engines.) Until recently, I did not know of any off-the-shelf product that solves the problem. Today, however, I discovered “Sta-bil Marine Formula” for ethanol fuels. Finally, there is hope! I spoke with a chemist at the company. I have been assured that if “Sta-bil Marine Formula” is added properly to E10, the fuel will remain fresh for 12 months. The chemistry in the blue Sta-bil (not the red Sta-bil) addresses both the oxidation issue and the moisture absorption issue. The red stuff still works fine if the fuel is stored in a sealed container...but such is not the case in the fuel tank of most vintage cars. Be aware and be happy that there is now a solution....but do nothing, and prepare to be sad.

Zach Merrill