Is E10 Ethanol Petrol OK for Historic Vehicles?

Malcolm McKay explains the increase in bioethanol in UK petrol.

Prophets of doom are suggesting that the increase in bioethanol content in UK petrol is going to kill classic cars and/or set them on fire. It is a danger if you have deteriorating, incompatible components in your fuel system, but it isn’t the end of the world: Brazilian historic vehicles have been running on 25% bioethanol since the 1970s. There are some issues, which we will discuss, but it certainly isn’t as big a nightmare as some suggest.

What is the current situation?

Until recently, all pump petrol was rated ‘E5’ and contained up to 5% bioethanol (some E5 contained no ethanol). Now it is E10 and contains between 5.5% and 10% bioethanol. Almost all 95 octane fuel previously contained near 5%, but the situation was – and remains – different for higher octane fuels. The “up to” element varies not so much between different fuels as between different parts of the UK. For example, Jet Ultra Premium is ethanol-free except in Yorkshire, Humber, Teesside and Scotland, where it contains 5% ethanol – and the situation is almost identical for Esso Synergy Supreme+, except that it may contain ethanol in North Wales, Cornwall and Devon too. This is because in areas where demand is lower, fuel companies rely on supplies from a third party that blends up to 5% ethanol in premium grades.

What is changing and why?

The government committed to a target of 9.75% of all transport fuels coming from renewable sources by the end of 2020. Bioethanol is fuel made from refining plants such as sugarcane, maize, potato, cassava and hemp. Waste organic materials such as waste wood are also increasingly used. Ethanol fuel is ethyl alcohol – the same type of alcohol that we drink, and logically so, as both are extracted from plant matter. And just as excess alcohol consumption can damage our internal tubes and systems, so it can with cars.

As is often the case, USA is ahead of UK, with 10% ethanol standard since 2011. Users report few issues other than having to adjust the timing – though that is really an octane issue. If the E10 fuel is of the same octane rating as the fuel you were previously using, no adjustment should be required. It’s also been in much of Europe for several years now, again with few issues reported.

It’s worth noting that ethanol itself is an octane booster, even though it’s currently being used in higher concentration in lower octane fuels – so removing it, as has become popular in some countries especially USA, is not necessarily going to help your engine run better. As well as the health and safety issues, removing it will lower the octane.

The Government has provided an E10 check website which is helpful for younger classic vehicles, but it’s worth noting that it errs (correctly) on the side of safety. For example, all Rover cars to the end of production are stated to be incompatible with E10 – simply because the Rover company no longer exists, so the government could not contact them to get confirmation of compatibility. However, Land-Rover does exist and confirmed that all its vehicles powered by Rover KV6 and K-series engines back to 1996 – which used identical fuel rails, O-rings and fuel line technology to Rover cars – are fully compatible. Owners of Rovers and MGs with those engines can therefore use E10 without fear.

What is the danger?

Some elastomers, plastics and composite materials used in pre-1996 car fuel systems are not compatible with petrol containing ethanol: it will gradually dissolve them. Cork, shellac, glassfibre-reinforced polyester and epoxy resins, nylon and polyurethane are on the ‘unsuitable’ list. Replacement with compatible materials is advised: paper, leather, Teflon, polyethylene and polypropylene are on the ‘OK’ list.

If any components in your fuel system are already old and deteriorating, ethanol will find them and accelerate the deterioration – to the point where you could rapidly have running problems and even leaks that could start a fire. It’s also worth noting that some fuel tank lining products used in the past to coat the inside of pinholed fuel tanks are not compatible with ethanol and cases have been reported of these breaking down, leaking and blocking fuel lines. New lining products are available which are resistant to ethanol.

Long-term storage of ethanol petrol can lead to corrosion in metal parts of fuel systems, as the ethanol element can absorb moisture if left in the system for a long time, such as over winter, in a humid atmosphere. Historic vehicles are more susceptible to this than modern cars, as their fuel systems are vented to the atmosphere, not sealed. Additives are available to counteract this, from suppliers such as HCVA Founding Partner Classic Oils

So what can we do?

1. Avoidance

Fuels with lower ethanol content (labelled E5) are still available. The government has pledged to keep them available for five years and this dispensation is renewable, but availability will depend on demand. Fuel companies warn that if consumption falls below commercial levels they will no longer supply it. The only E5 fuels available are the higher octane ones – 97 or 99 octane – but this is not a problem as all petrol vehicles will run on them and, if properly adjusted, will run more efficiently on these fuels, counteracting to some extent their higher cost. If you shop around, the cost premium is not huge – most supermarkets stock 97 octane E5, though sometimes only at one pump.

For older engines with 9:1 compression or higher, that were originally designed for 100 octane fuel, 99 octane fuels are available – Tesco Momentum 99, Esso Synergy Supreme+ 99 and Shell V-Power 99 contain no more than 5% ethanol and Esso confirms that its 99 octane fuel is still ethanol-free except in Devon, Cornwall, North Wales, North England and Scotland. Using lower octane fuel in a 9:1 engine either requires retarding the ignition (which can lead to other issues) or the addition of an additive, which almost always works out more expensive than buying the 99 octane fuel if it can be found; some engines will accept 97 octane without complaint/adjustment, some won’t.

Additives are great for improving fuel, such as providing valve seat protection on engines with cast iron heads having soft valve seats, and for increasing octane. It’s much more difficult to make an additive to correct negative effects of something that is already in the fuel.

2. Additives

If additives are your preferred option, beware of the snake oil salesmen. Only buy from reputable businesses with an established history of serving the historic vehicle market. For example, tin pellets thrown in the petrol tank are NOT a cure-all for everything from unleaded fuel to E10.

Guy Lachlan of Classic Oils confirms that additives offering protection from the negative effects of ethanol in fuel will ONLY protect against corrosion from water absorbed by the fuel – they will not protect against the harmful effects on incompatible materials in the fuel system.

3. Conversion

Converting your classic vehicle to tolerate E10 fuel will be the best long-term option for most owners doing higher mileages. Kits will soon be available, if they’re not already, for DIY conversion of popular classic vehicles and marque specialists are already well prepared to carry out conversions for you.

First, it is important to replace incompatible materials (listed above) in the fuel system: these will mostly be seals, hoses and gaskets. If you don’t do this, you may experience no problems, especially if your hoses, seals etc are relatively new – but gradually they will deteriorate internally and begin to cause running problems as degraded materials are carried through the system, blocking jets etc. There is also a danger of ultimate failure of hoses and seals, causing fuel leaks.

Second, it may be necessary to re-route fuel lines away from engine hot-spots, as E10 (like most modern fuels) is more volatile than leaded petrol was and more prone to cause fuel vaporisation. This has become a major issue for some historic vehicles in the last decade. All modern vehicles have sealed fuel systems with fuel cooled by constantly circulating back to the tank, so fuel suppliers have allowed fuel volatility to increase dramatically. It is now at levels that vaporise far too easily in historic vehicles, where fuel may sit for some minutes in carburettor float chambers just above a hot exhaust pipe, when in traffic or stationary. Using E5 fuel, adding heat shields and re-routing and lagging fuel lines all help to reduce this problem.

Third, it may be necessary to richen the mixture fractionally, as the ethanol mix burns slightly leaner – by 3.6%, so if your engine is set slightly rich already (as many are) there’s no need to alter it.

Add a clear plastic filter in the fuel line before the carburettors (ideally in a cool place where it will not increase vaporisation issues) and keep an eye on it, so that you will get advance warning of potential problems if rust or rubber particles are coming through from the tank and pump.

When touring, carry a spare fuel pump diaphragm and metal carburettor float(s) so that you can easily fit them at the roadside if problems arise.

Some suggest that fuel tanks should be replaced with ethanol-compatible tanks. While this would be sensible if you’re replacing the tank anyway, in reality replacement is only necessary if you have a tank made of glassfibre (as in some 1960s classic cars and motorcycles) or an incompatible plastic. Corrosion will take place inside a half-empty steel fuel tank whatever the fuel used if left standing for months in a humid atmosphere – it is best to brim the tank before short-term storage and to use ethanol-free fuel if possible or at worst E5, with the anti-corrosion additive.

If you routinely store your vehicle for long periods such as over winter, fit a fuel tap between the fuel tank and the pump (if one is not already fitted). When storing the vehicle, run it with the tap switched off until all fuel in the carburettor(s) and pump is used up. This will reduce the risk of ethanol attacking rubbers in the pump and carbs, and will also avoid the hard residue left when modern fuels evaporate, which then blocks jets and requires laborious cleaning before the vehicle will run again after storage.

High ethanol experience

HCVA Director Malcolm McKay comments, “Back in 2001, I competed in the Inca Trail rally in my 1955 TR2: the rally started and finished in Rio de Janeiro, so we had a few tankfuls of Brazilian petrol containing at least 25% ethanol. I had no problems whatsoever from this fuel, then or since, though there were reports of running problems on a few of the other cars that may (or may not) have been caused by the fuel. I had fully rebuilt my car less than 10 years earlier, so all rubber parts, carburettor floats etc had been new at that time, which undoubtedly helped.”