Introduction of E10 Petrol as the standard for fuel across the UK

As I write this article in early April a consultation exercise was launched by Her Majesty’s Government on 4th March about its proposal to introduce E10. The six-week consultation period was due to end on 18th April and the results may be out by the time this issue is published. With the unrelenting pressure on governments to be seen to be taking steps to act as a result of climate emergency declarations, there can be little doubt that the proposal will go ahead, hence the editor’s choice to omit the word ‘proposal’ in the title of this article.

Typically, fuel companies currently blend petrol with up to 5% bioethanol and diesel with 7% biodiesel. The Government has a target to ensure that 9.75% of all transport fuels must come from renewable sources by the end of this year under its “Renewable Transport Fuel Obligation”. It believes that a move to standardising E10 fuel will be equivalent to taking 350,000 cars off the road each year. The Department for Transport estimates that this may cut CO2 emissions for transport by 750,000 tonnes per year.

It looks as though the introduction of E10 in the UK may be challenging as it has been reported that the only domestic refinery for the additive has closed and the environmental costs of shipping additives from other parts of the world would negate the environmental benefit.

The harmful side effects of ethanol on fuel systems are well catalogued, but is it such a monster that it has been portrayed as? Read this article from Paul Ireland.

E10 – The Good, the Bad and the Ugly

The UK Government is planning to introduce petrol containing 10% ethanol (alcohol) next year. This is referred to as E10. Most of what has been written on this subject does not tell the whole story, focusing on the potential damage this fuel can cause. This article aims to allay owners’ fears, especially for those with classic vehicles.

It is based on research performed at Manchester University using an engine designed in the late 1930s. For anybody wanting to find out the full story, the results and recommendations have been published in a very readable book, Classic Engines, Modern Fuel – The Problems, the Solutions.

Question – why add ethanol to petrol in the first place? Government policy to reduce carbon emissions from vehicles is the reason. The carbon in the ethanol comes from renewable sources. It is a by-product of the sugar industry. When running on E10 a petrol engine still emits the same amount of carbon into the atmosphere. However, only 90% of it comes from fossil fuel. E10 effectively reduces the carbon load by 10%.

Adding ethanol to petrol is not new. Cleveland Discol was introduced in 1928 and sold until 1968. The good news is, after 40 years of use in what are now today’s classic cars, Discol did not appear to cause serious problems.

The Good

Modern petrol is both physically and chemically different from classic petrol. Physical differences include a lower boiling point. Chemical differences include the addition of ethanol. Both of these alter the way a classic engine runs on modern fuel.

The Manchester tests showed modern fuel increases the severity of a phenomena called Cyclic Variability, making it worse at the RPM and throttle settings used when driving in normal traffic.

All petrol engines suffer from Cyclic Variability. It reduces power output and increases petrol consumption. Worst still, it can cause serious damage, burning valves and pistons and destroying the big end bearings. A high level of Cyclic Variability is very damaging for an engine. Modern petrol makes this level worse. The rankings of the fuels tested at Manchester are shown on the diagram. Three of the top six best performing fuels contained ethanol (shown in orange), the other three (shown in grey) were specialist fuels. Fuels without ethanol (shown in blue) ranked poorly. The test engine ran considerably better on the petrol containing ethanol as these reduced the level of Cyclic Variability.

E10 ranked 3rd best, scoring twice as many points as non-blended fuels.

The good news is that E10 promises to reduce potentially very expensive damage to an engine. A positive fact other articles do not make clear.

The Bad

A great deal has been written about the damage ethanol can cause to fuel system components. It rots older non-metallic components such as rubber hoses, seals, diaphragms and plastic floats. Also, it contains oxygen which weakens the mixture. E10 makes these problems worse.

Rotting hoses can be a serious problem, especially if they go undetected. Petrol leaks around the engine is the last thing you want. Petrol is highly flammable and leaks are a serious fire risk. Age, as well as ethanol, causes hoses to rot. In any case, it is worth replacing old hoses, etc. Ethanol proof replacements are now available for most vehicles.

This problem is not as bad as it would first appear. Fitting replacement hoses, etc., is a lot cheaper than rebuilding an engine!

The other problem, that ethanol contains oxygen, is something to be aware of. This causes an engine tuned to run on normal petrol to run weak. Insufficient petrol enters the cylinder. Like Cyclic Variability, weak running can cause serious damage to an engine.

The good news is that variable jet carburettors such as SU and Stromberg only need minor adjustments to offset the effects of E10. Unfortunately, these adjustments are harder with fixed jet carburettors such as Weber and Zenith. These may need new jets or emulsion tubes.

Modern electronic fuel injection systems are able to adjust by themselves.

One interesting result of the Manchester tests was that petrol containing ethanol increased the engine’s power output. This is because it reduces the degree of the damaging Cyclic Variability. As a result, classic engines running on E10 will possibly deliver more MPG, not less, as some authors have suggested.

The bottom line is that E10 does cause some problems. As long as owners are aware, addressing them is neither difficult nor expensive.

The Ugly

The ugly face of ethanol blended petrol is its ability to dissolve metal. The picture that follows shows two samples. One a piece of steel, the other part of an aluminium float chamber. These were stored in water that had come in contact with ethanol blended petrol. Even after only 4 months, the level of corrosion is severe. When water comes into contact with ethanol blended petrol it draws the ethanol out of the petrol, making the water acidic. It is this acid that attacks the metal components. This problem is as serious with current petrol blends as it will be with E10. All it needs is a single drop of rainwater getting into the fuel system.

Is this something to worry about? Not really. As long as you are very careful not to get any water into your petrol system; something easier said than done, especially with older cars or motor bikes where the filling cap is on the top of the tank. Petrol filling caps or tickler pins in the carburettors can let in water. Especially if driving in heavy rain.

Unfortunately, inhibitors sold to protect against ethanol will not help in this situation. Classic Engines, Modern Fuel – The Problems, the Solutions describes some ways of avoiding this problem.


E10 is not as bad as some people make out. Older engines run better on ethanol blended petrol, reducing the expensive damage Cyclic Variability can cause. While there are some issues, they can be addressed with care and low cost solutions.

Perhaps the forthcoming introduction of E10 is not so bad after all.

The following is a link to the website that Paul has created, where you read reviews of the book and purchase a copy, register and log in to compare advance curves, and participate in the bulletin board.

Introduction of E10 (continued)…….(back to the Editor).

I should have pointed out, when referring to the consultation exercise, that the Department for Transport recognises the issue of vehicle compatibility with the introduction of E10. The relevant extracts from the consultation paper are as follows:

“……Currently around 95% of petrol cars used in the UK can use E10, but around 700,000 are not warranted by their manufacturers to use E10. This number is expected to decrease as vehicles come to the end of their life. However, some classic and cherished vehicles that are not advised to use E10 will remain in use.

The prolonged use of E10 fuel in those older and classic vehicles not under manufacturer warranty can cause corrosion of some rubbers and alloys used in the engine and fuel systems. For those vehicles, the Department remains committed to ensuring that E5 is retained as a protection grade, if E10 is introduced.”

However, if I cast my mind back to the widespread introduction of unleaded petrol, it didn’t take long for the leaded variety to disappear from the forecourts. Against this background, will the petrol companies be willing to support the miniscule demand for E5?

A couple of examples of the harmful effects of E5 were sent to me by Roland Crisp, owner of TC5951. Here’s what Roland said in a recent e-mail to me:

“Not only do I enjoy my TC, I am also the owner of several Classic English and Japanese motorcycles.

Due to a house move 18 months ago and until recently no garage, I was forced to lay-up the bikes.

I have enclosed a photo of two petrol taps with integral filters, or what remains of the filters. In the photo, the one on the left is plastic and as you can see, the filter gauze is missing and the other tap had a copper filter which has almost totally disappeared.

Both were eaten away by the fuel, despite an additive that was supposed to protect them from the effects of ethanol in E5 petrol.

The knock-on problem was that the residue from the chemical reaction with the plastic or copper ended up blocking jets in the carburettors, and in some case, blocking the taps themselves.

When I drained the tank that had had the copper-filter the fuel was emerald green, very pretty but I think I now know where some of the copper went.

So, be warned, your pride and joy can be affected in the same way. So perhaps, as I have done in the present Covid-19 lockdown, it is prudent to drain the fuel?

I understand that in most parts of Great Britain, but not all, Esso Synergie does not yet have ethanol added to it, so that may be the way to go?

Looking forward to E10 fuel next year!”

Ed’s note: Paul Ireland puts this down to an ingress of water.

The two petrol taps referred to in the text.

The petrol which was drained from the tank with (what was left of) the copper filter.

Editor’s further note: Roland’s mention of Esso and Paul’s reference to Cleveland Discol prompted me to look up some historical facts. I’m old enough to remember Cleveland Discol being sold on the forecourts, but what I didn’t know is that the Cleveland filling stations were re-branded as Esso in 1973.

Cleveland Petroleum Products was established at Trafford Park, Manchester and Preston in 1920. In 1934 the company was given the rights to use the trademark Discol in exchange for an undertaking to buy the alcohol needed from The Distillers Company. The latter was a public company formed in 1877 by a combination of six Scotch whiskey distilleries. It grew and grew, being acquired by Guinness in 1986; then in 1987 coming under the umbrella (with Arthur Bell and Sons) of United Distillers (both owned by Guinness) and finally, in 1997, coming under Diageo.

3 thoughts on “Introduction of E10 Petrol as the standard for fuel across the UK

  1. irelandp says:

    Yes, any petrol that contains ethanol, no matter what concentration, will suffer the same effect if water gets into it. The water draws the ethanol out of the petrol, increasing its acidity. As we do not know if what you are putting into your tank contains ethanol, the advice, Be VERY CAREFUL and make sure you get no water into your tank.

    I now drain my tank every other year and leave it empty over winter to “dry out”.

  2. M Wingrove says:

    Draining the fuel system is all very well, but condensation in fuel tanks & carburettors is common.

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