E10 fuel is now the default petrol at the pumps. Here’s everything you need to know about this higher-ethanol fuel
Arriving in 2021 in a flurry of news, controversy and debate, E10 fuel has become the standard form of petrol available on UK forecourts. The previous standard, E5, has now been superseded and is only available in the form of more expensive premium-grade fuels.
As its name suggests, E10 petrol contains up to 10 per cent ethanol, twice the proportion of the E5 grade which has been the standard for the last decade. The issue of ethanol in fuel has long been a hot potato in the classic car world but at the lower concentration of the E5, fuel has proved not to be a problem in practice. However, the E10 grade has people worried about its effects on older cars.
There are two big issues with ethanol fuels and older cars. The first is that ethanol can have a corrosive effect on metal, plastic and rubber parts in the fuel system. The results of this can range from inconvenient, like sticking carburettor floats, to dangerous, such as when fuel lines perish.
Crucially, not all vehicles will have problems and rather like the introduction of unleaded fuel back in the ’80s, some will be perfectly happy on the new fuel and some will need modification.
The second issue with the E10 fuel and something which is more of a problem for classic cars than everyday modern vehicles is that the ethanol is hygroscopic, meaning it tends to absorb water. Clearly the longer a car is left standing idle, the bigger an issue this will be, with any moisture in the fuel only adding to potential issues.
Meanwhile, there are suggestions that some two-stroke engines – from motorcycles to old Saabs and chainsaws – are also ill-suited to the higher ethanol content found in the new fuel.
Why E10 petrol?
In theory the use of E10 petrol is an environmental move, intended to reduce the fossil fuel component of vehicle fuels and therefore combat climate change.
Rather than emissions or air quality, the goal is reduced CO2 emissions and it’s thought that by doubling the proportion of the renewable component in the fuel (the ethanol) a 750,000-tonne reduction in CO2 is achieved – the equivalent of taking 350,00 cars off the road.
It’s not all good though. The fuel is slightly less energy dense, meaning an economy reduction of up to 1%, but what’s not widely known is that since 2016 new cars have been certified for emissions and performance using E10 fuel.
What can classic owners do about E10?
Owners of modern classics can use the government’s online checker tool which uses information supplied by car makers as to the suitability of the fuel system. Information is patchy but has improved since the online check was first offered and for many brands the system will go as far back as the early 90s.
Some marques, especially the German brands, go back even further: Volkswagen for example simply states that all its engines can run on E10 fuel except for a few FSI units from the early 2000s, while BMW flatly states that all its cars can use E10.
More modern future classics also escape the issue, since all new cars have been capable of using E10 fuels since 2011.
Clearly though, this doesn’t help owners of older cars, so what options do owners of traditional classics have? Well the good news is that the technology exists to upgrade the fuel systems to cope with the new fuel.
In truth, it’s good practice to renew ancient fuel lines as a precaution in any case. Modern fuel hose sold by a reputable supplier is rated for use with E10 (see Modifying for E10 below).
See my article on my experiences with fuel hose and ethanol fuel here
However, this may not be necessary for some owners, since the regulations require larger forecourts selling two grades of petrol to continue selling E5 fuel.
This will be offered only in the more expensive Super Unleaded grade however, which brings its own problems: even the bigger petrol stations often only have a single Super Unleaded pump, and in rural areas it may be hard to find a retailer large enough to stock it. Super Unleaded is also a more expensive fuel, with the price gap potentially set to widen further in time.
We’ll be keeping a close eye on further developments, but in the meantime the options for drivers of older cars are clear: if your car isn’t covered by the DfT online checker or is deemed unsuitable for E10, then you can either use the more expensive Super Unleaded or can update the fuel system and use a fuel stabiliser additive when the car is left for long periods.
A few of our customers have asked us about “Ethanol” in the standard UK’s petrol on their Mustangs. Yep, that very word ‘Ethanol’ the chemical formula which is ‘C2H5OH’ strikes fear into any classic car owner. Ask us the chemical formula should be ‘DEV1L’s juice. Many questions since the switch over to E10 in September this year here in the UK. A few problems have arisen from their old fuel lines now under attack the Ethanol, and leaking. If you’re not careful, you could be in for some big bills! Despite what people think and say about us, here we are going to try and stop you spending out large wads of cash with us believe it or not.
We have done a little research and collated some pointer and facts for you;
Ethanol is an alcohol substance, those properties will dry out the rubber components in a fuel system. This leads to cracking and brittle fuel lines, floats, seals and diaphragms, caps off’s etc.
Ethanol is corrosive when in comes into contact with certain materials within the fuel delivery systems and its related storage. This will be things like the flexible joining parts, rubber compounds and also the more worrying aspects of the zinc and aluminum alloys used in carburetors. Yep, your nice new shiny carb will slowly disintegrate inside out.
Ethanol is ‘hydrophilic’. In other words it loves water. Because of the water absorbency properties, the water content enters fuel containers when they are filled up, that’s your fuel tank, jerry cans, plastic petrol cans etc. Once water is in the fuel it forms a chemical mix that causes corrosion of internal parts. As the fuel level in your fuel tank or container drops, water condenses on the cool surfaces of the container, droplets form and run down into the fuel where the ethanol absorbs it.
Ethanol is also a solvent in older or classic car engines. Not such a bad thing you say? Well, the ethanol begins dissolving the varnish and other deposits in your tank and fuel lines. These deposits are then carried to the carburetor or injection system where they can clog the small or tiny orifices involved. The results of which could cause all sorts or problems, over fueling, fuel starvation, stuck floats, blocked jets, engine stumbling, idle issues, pick up issues and so on.
FBHVC clarification on E10 fuel and forecourt labelling for historic vehicles
After an extensive consultation process, the Department for Transport has introduced legislation to mandate E10 petrol as the standard 95-octane petrol grade from 1 September 2021 and in Northern Ireland, this will happen in early 2022. They will also require the higher-octane 97+ ‘Super’ grades to remain E5 to provide protection for owners of older vehicles. This product will be designated as the ‘Protection’ grade. The change in fuel applies to petrol only. Diesel fuel will not be changing.
Petrol pumps now show new labels designating the grade, the maximum ethanol content and an advisory cautionary notice. Other information regarding the introduction of E10 petrol may also be provided by fuel retailers such as the ‘Know your Fuel’ sticker (shown at the foot of this article).
For some time, service station pumps have had E5 and B7 labels consistent with the BS EN16942 standard that has been adopted across Europe. This standard also sets out the labelling requirements for other renewable fuel grades such as E85, B20, B30, etc. that can be found across Europe either on service station forecourts or for captive fleet use.
At the filling station
At the petrol station, a circular ‘E10’ or ‘E5’ label will be clearly visible on both the petrol dispenser and nozzle, making it easy for you to identify the correct petrol to use together with the warning text “Suitable for most petrol vehicles: check before use”
The ‘E10’ and ‘E5’ labels look like this:
Labels on modern vehicles
New vehicles manufactured from 2019 onwards should have an ‘E10’ and ‘E5’ label close to the filler cap showing the fuel(s) they can use.
What fuel should I use?
Almost all (95%) petrol-powered vehicles on the road today can use E10 petrol and all cars built since 2011 were required to be compatible.
If your petrol vehicle or equipment is not compatible with E10 fuel, you will still be able to use E5 by purchasing the ‘super’ grade (97+ octane) petrol from most filling stations.
The Federation recommends that all vehicles produced before 2000 and some vehicles from the early 2000s that are considered non-compatible with E10 – should use the Super E5 Protection grade where the Ethanol content is limited to a maximum of 5%.
To check compatibility of vehicles produced since 2000, we recommend using the new online E10 compatibility checker: https://www.gov.uk/check-vehicle-e10-petrol however, please note that many manufacturers are missing and there are some discrepancies regarding particular models.
Ethanol is an alcohol derived from plants, including sugar beet and wheat. Increasingly, waste products such as wood are also being used to manufacture ethanol. Therefore, it is renewable and not derived from fossil fuels.
Why are we using it?
Principally ethanol is being added to fuel in order to reduce carbon emissions as Britain heads towards its target of net zero emissions by 2050. According to Government experts, this will reduce greenhouse gases by 750,000 tonnes per year which, they say, is the equivalent output of 350,000 cars. The move will bring the UK into line with many European countries which have been using E10 fuels for a number of years already. In some parts of the world, such as South America much higher levels of bioethanol have been in use since as early as the 1970s.
What might happen?
Corrosion / Tarnishing of metal components
Elastomer compatibility – swelling, shrinking and cracking of elastomers (seals and flexible pipes) and other unsuitable gasket materials
Air/fuel ratio enleanment
Some historic vehicles use materials in the fuel systems that are damaged by ethanol. These include some cork, shellac, epoxy resins, nylon, polyurethane and glass-fibre reinforced polyesters. In later cars these have largely been replaced with paper gaskets, Teflon, polyethylene and polypropylene which are all unaffected by ethanol. Very old leather gaskets and seals are also resistant to ethanol.
As the ethanol molecule is smaller and more polar than conventional petrol components, there is a lower energy barrier for ethanol to diffuse into elastomer materials. When exposed to petrol/ethanol blends these materials will swell and soften, resulting in a weakening of the elastomer structure. On drying out they can shrink and crack resulting in fuel leaks.
If your fuel system has old hoses or any degradation of components, then ethanol may appear to advance these problems very quickly. You may experience leaks or fuel “sweating” from fuel lines. Some fuel tank repair coatings have been found to breakdown and clog fuel systems, although there are plenty of ethanol resistant products on the market.
What can we do?
The most important thing is to ensure your fuel system components are regularly inspected and renewed as part of a routine maintenance programme for your historic vehicles. Ultimately owners should look to renew fuel system components such as hoses, seals and gaskets with ethanol safe versions as a long – term solution and more of these are entering the market through specialists every day.
If you should decide to make the necessary vehicle fuel system modifications together with the addition of an aftermarket additive to operate your classic or historic vehicle on E10 petrol. The FBHVC strongly recommends that you regularly check the condition of the vehicle fuel system for elastomer and gasket material deterioration and metallic components such as fuel tanks, fuel lines and carburettors for corrosion. Some plastic components such as carburettor floats and fuel filter housings may be become discoloured over time. Plastic carburettor float buoyancy can also be affected by ethanol and carburettors should be checked to ensure that float levels are not adversely affected causing flooding and fuel leaks.
Ethanol is a good solvent and can remove historic fuel system deposits from fuel tanks and lines and it is advisable to check fuel filters regularly after the switch to E10 petrol as they may become blocked or restricted. If your vehicle is to be laid up for an extended period of time, it is recommended that the E10 petrol be replaced with ethanol free petrol which is available from some fuel suppliers. Do not leave fuel systems dry when storing, as this can result corrosion and the shrinking and cracking of elastomers and gaskets as they dry out.
Ethanol contains approximately 35% oxygen by weight and will therefore result in fuel mixture enleanment when blended into petrol. Petrol containing 10% ethanol for example, would result in a mixture-leaning effect equivalent to approximately 2.6%, which may be felt as a power loss, driveability issues (hesitations, flat spots, stalling), but also could contribute to slightly hotter running. Adjusting mixture strength (enrichment) to counter this problem is advised to maintain performance, driveability and protect the engine from overheating and knock at high loads.
Modern 3-way catalyst equipped vehicles do not require mixture adjustment to operate on E10 petrol because they are equipped with oxygen (lambda) sensors that detect lean operation and the engine management system automatically corrects the fuel mixture for optimum catalyst and vehicle operation.
Additives and vehicle storage.
Ethanol has increased acidity, conductivity and inorganic chloride content when compared to conventional petrol which is typically pH neutral. Ethanol can cause corrosion and tarnishing of metal components under certain conditions. These characteristics are controlled in the ethanol used to blend E5 and E10 European and UK petrol by the ethanol fuel specification BS EN15376 in order to help limit corrosion.
Some aftermarket ethanol compatibility additives claim complete protection for operating historic and classic vehicles on E10 petrol. The FBHVC is not aware of, or has tested any additives that claim complete fuel system protection with respect to elastomer and gasket materials for use with E10 petrol. The FBHVC therefore recommends that elastomer and gasket materials are replaced with ethanol compatible materials before operation on E10 petrol.
However, corrosion inhibitor additives can be very effective in controlling ethanol derived corrosion and are recommended to be added to ethanol in the BS EN15376 standard. It is not clear if corrosion inhibitors are universally added to ethanol for E5 and E10 blending so as an additional precaution it is recommended that aftermarket corrosion inhibitor additives are added to E5 and E10 petrol.
These aftermarket ethanol corrosion inhibitor additives often called ethanol compatibility additives are usually combined with a metallic valve recession additive (VSR) and sometimes an octane booster and have been found to provide good protection against metal corrosion in historic and classic vehicle fuel systems.
What happens if I fill up with E10 by accident?
Don’t panic – your car will continue to run, just fill up with E5 at the next opportunity and avoid storing your vehicle for long periods with E10 fuel.
E5 petrol can contain between 0 and 5% by volume ethanol. Other oxygenated blend components may also be used up to a maximum petrol oxygen content of 2.7%. There is a variation at the pumps, not just between brands but also between different areas of the country, some will contain a lot less but the absolute maximum is capped at 5%.
E10 petrol contains between 5.5 – 10% ethanol by volume. Other oxygenated blend components may also be used up to a maximum petrol oxygen content of 3.7%. Again, there is a variation at the pumps, not just between brands but also between different areas of the country, some will contain a lot less but the absolute maximum is capped at 10%.
It should be noted that some Super E5 Protection grade fuels do not contain Ethanol as the E5 designation is for fuels containing up to 5% Ethanol. To re-iterate, product availability varies by manufacturer and geographical location.
The renewable content of diesel fuel will not be changing and service station fuel pumps will continue to be labelled as B7, designating a biodiesel, Fatty Acid Methyl Ester (FAME) content of between 0 and 7% by volume. New vehicles manufactured from 2019 onwards should have a ‘B7’ and or higher content label close to the filler cap showing the fuel they can use. The ‘B7’ label looks like this:
Please find below a list of branded fuel suppliers providing E5 protection grade fuel and links to their websites where more information can be obtained: (please note more may be available and the list will be updated accordingly)
BP: E5 Protection grade – bp Ultimate Unleaded 97 with ACTIVE technology
Looking back over a quarter of a century or perhaps longer, there have been changes to:
Octane quality: loss of “two star” petrol in 1989-1990
Lead in petrol: withdrawal of leaded petrol at the end of the twentieth century
Boiling characteristics of petrol (also called volatility): progressive increase in the use of very volatile components in the fuel blend
Sulphur content: reduction to trace levels (10 mg/kg) denoted sulphur free in 2009
Blending of biofuels:
Use of ethanol in petrol: initially at 5% volume, increasing to 10% volume in September 2021, although a 5% volume high octane protection grade will still be available.
Use of biodiesel in diesel: up to 7% volume FAME
Synthetic fuels: announcements of pilot projects to manufacture liquid fuels in 2020 that can run in internal combustion engines made from hydrogen from water and carbon capture from the atmosphere.
The Federation has maintained a watching brief throughout this period and has sought to understand the concerns of its members, to quantify potential problems for older vehicles and to suggest possible remedies where difficulties have been encountered. It is worth looking at a summary of concerns rising from these fuel changes, and Federation actions. Concerns have been expressed by owners and drivers of historic vehicles whenever changes have occurred. Sometimes these concerns have proven to be ill-founded, while on other occasions, there have been examples of real problems which have necessitated action on the part of the owner to prevent damage, or to maintain normal operation, or possibly both. Concerns linked to the fuel changes identified above are discussed below:
Ethanol effects in more detail
The Federation has identified three operational aspects relating to the addition of ethanol to petrol:
Some elastomers, plastics and composite materials are not compatible with petrol containing ethanol. Where problems are experienced, incompatible materials in the fuel system should be replaced with compatible alternatives.
Acknowledgement and thanks to CONCAWE who provided the above data.
Long-term storage of petrol-ethanol mixtures (eg. over a winter period) can lead to corrosion in historic vehicle fuel systems. Following tests, a number of corrosion inhibitor additives which were effective at protecting fuel system metals were identified by the Federation and previously endorsed. The use of corrosion inhibitor aftermarket additives is now well established in historic vehicles and due to the changing nature of individual supplier product formulations, it is no longer possible to provide a listing of endorsed additives.
There is no evidence that the addition of ethanol to petrol directly affects combustion adversely, but ethanol does have a
leaning effect; fuel mixture strength becomes slightly weaker, and this is particularly true for higher ethanol blends. Petrol containing 10% ethanol for example, would result in a mixture-leaning effect equivalent to approximately 2.6%, which may be felt as a power loss, but also could contribute to slightly hotter running. Adjusting mixture strength (enrichment) to counter this problem may prove beneficial. The addition of ethanol to petrol increases the volatility, however this is taken into account when the petrol is manufactured so that the finished ethanol/petrol blend has the same volatility as petrol not containing ethanol and meets the BS EN228 petrol standard requirements. It should be noted however, that switching between ethanol containing petrol and non-ethanol containing petrol will result in the mixture in the fuel tank having a higher volatility, which may cause vapour locking problems and should be avoided if possible.
Matt Tomkins, an associate of FBHVC and Projects Editor of Practical Classics Magazine carried out a study of carburettor component degradation in varying concentrations of petrol/ethanol mixes whilst studying as an undergraduate student at Oxford Brookes University. This study was submitted as his undergraduate thesis and Matt has been kind enough to give FBHVC permission to reproduce it here. You are respectfully requested to respect his copyright of this interesting work.
There have been a number of announcements in 2020 with respect to E-Fuels that are hydrocarbon fuels produced from non-fossil sources. Renewable electricity is used to produce hydrogen from water by electrolysis and carbon is captured from the atmosphere (CO2) and combined to produce a liquid fuel. Synthetic fuels have an advantage over conventional biofuels in that they do not compete with food supply or for land use. Whilst synthetic fuels have been produced from fossil hydrocarbon sources over many years and the processes are well understood, these fuels are unlikely to be available in volume for many years to come due to the high levels of renewable electricity required and the difficulty and cost of filtering CO2 from the atmosphere, but do offer the hope that liquid fuels with their high energy density will continue to be available in the future.
Concerns were expressed about the loss of low octane fuels with, in the view of some, “too much” octane for old engines. Study has shown that this concern is baseless. In effect, it is impossible to have too much octane quality, and older engines can operate very satisfactorily on a fuel with octane quality greatly exceeding their natural requirement.
In the mid 1930s Research Octane Numbers (RON) were around 70 which allowed compression ratios to increase to about 5.5:1. Many 1950s vehicles, for example, probably require no more than 80 RON petrol, if such a product were available, yet will run well on 95 or 97+ RON petrol. Furthermore, most pre-war cars were designed to tolerate even lower octane fuels, yet will also run well on today’s 95 or 97 RON petrol. Octane requirement should therefore be seen as a minimum requirement to ensure the correct operation of the engine. More information on octane is provided in the Operating problems and supplementary information section.
The withdrawal of lead from petrol raised very real concerns about engine damage from exhaust valve seat recession (VSR) in older engines with cast-iron cylinder blocks and heads and also aluminium cylinder heads fitted with soft valve seat inserts. The Federation commissioned engine tests to assess the level of protection against VSR provided by fuel additives for use in historic vehicles with unsuitable metallurgy. Those additives providing the required level of protection were afforded a Federation endorsement, in a scheme which has been a good example of a successful programme of intervention to assist Federation members to overcome potentially harmful side effects from the change in fuel specification inaugurated by the Government. In addition to defining reliable additive-based treatment options to counter the unleaded threat, the Federation also assisted with information about preventative options in the form of hardened exhaust valve seat inserts to overcome the VSR problem. Furthermore, the Federation lobbied successfully to secure an EU concession for the sale of leaded petrol in the UK, a concession which survives to this day, although current sales outlets are few in number, and the uptake of the product is quite small. In part, the difficulty of setting up a satisfactory distribution for leaded petrol for the use of historic vehicles, is proof of the general truth that a good distribution system for specialised fuels for historic road vehicles is not a viable commercial proposition.
The use of VSR aftermarket additives is now well established in historic vehicles and due to the changing nature of individual supplier product formulations, it is no longer possible to provide a listing of Federation endorsed additives. VSR additives containing potassium, phosphorous, manganese (MMT) and sodium have all been shown to be effective in preventing valve seat recession under all but the most severe operating conditions. It should be noted that the above VSR additives are not recommended for use in catalyst equipped vehicles and can result in catalyst fouling and oxygen (lambda) sensor failure.
Retailers offering leaded petrol (specification equivalent to the old 4-star petrol):
As well as being a member of the FBHVC, producers, importers and distributors of leaded petrol must hold a permit from the Secretary of State of Transport in order to comply with Motor Fuel (Composition and Content) Regulations 1999 and subsequent revisions.
In order to apply for a permit please contact International Vehicle standards at the Department for Transport at firstname.lastname@example.org
In order to preserve historic and classic vehicle operation on the road and avoid environmental criticism, the Federation encourages all historic vehicle owners to cease using leaded petrol. Those engines that cannot be converted to hardened valve seats can use non-lead based VSR additives which provide adequate protection under all but the most extreme load conditions such as motor racing. The Federation will therefore no longer list fuel suppliers providing lead additives and leaded petrol.
Boiling characteristics (fuel volatility):
Concern that a progressive increase in the use of high volatility blending components in petrol over many decades was identified by the Federation, with many owners of historic vehicles affected by the mystifying but frustrating effects on vehicle performance which can result from the mis-matching of fuel volatility to the needs of older fuel systems. Explanations of the problem were accompanied by simple common-sense solutions which allowed owners to make minimum modifications to their vehicle fuel systems to offset the effect of higher volatility fuels.
The boiling range of petrol has not changed much since the introduction of the first motor vehicles at the end of the 19th century, typically boiling between 30°C and 200°C. Whilst the boiling range has not changed a great deal over the years, the front end of the boiling range has seen an increase in lower-boiling components that increased the vapour pressure of the petrol and the likelihood of vapour bubbles forming in the fuel system causing vapour lock and driveability problems.
Since 1993 petrol volatility has been declining in an effort to reduce evaporative emissions from vehicles. Vapour pressure a measure of volatility is determined at 37.8°C (100°F) and is a good indicator of a fuels propensity to cause vapour locking in older vehicle fuel systems.
Summer Vapour Pressure (kPa)
Winter Vapour Pressure (kPa)
Modern summer volatility petrol sold in the UK has a maximum vapour pressure of 70 kPa and in mainland Europe 60 kPa which reflects the difference in summer temperatures. Higher volatility components such as butane are used in the winter, spring and autumn periods as they provide a cost effective source of octane and also help cold starting. A parameter called the Vapour Lock Index (VLI) a calculation using vapour pressure and distillation characteristics which has been developed from vehicle operability data is also applied during the spring and autumn periods to limit vehicle operability issues such as vapour locking.
The seasonal adjustment of petrol volatility is very important for good engine operation all year round, however it can cause problems such as vapour lock in older low fuel pressure vehicle fuel systems. To help owners of historic vehicles it is important to understand how petrol quality is varied in the UK during the year to enable the optimum grade to be purchased for best operation.
The European petrol standard EN228 allows national standardisation bodies to select appropriate volatility and distillation characteristics to suit their local climate conditions.