E10 Myth & Fact

Understand what E10 fuel is, how it might affect the way you look after your classic and why there is so much nonsense and scare mongering about it.

What is it?

E10 fuel has been in both the classic and mainstream press a lot. Pump fuel is made up from an awful lot more than just fractionally distilled mineral oil, part of that is ethanol. Currently the UK standard for ethanol content in normal unleaded fuel is less than 5%, so at the time of writing it is labeled as E5. Ethanol is a fuel produced from crops, by using it we reduce the carbon footprint of every tankfull.  The government is keen to increase the amount of ethanol in our fuel because it decreases our dependence on OPEC nations and it could reduce the national CO2 emissions by 750,000 tonnes a year. In September 2021 the UK standard for ethanol content will increase to 10% on standard unleaded, but will remain at less than 5% for super or premium unleaded.

What is the issue with a higher ethanol content?

Firstly, there is nothing we can do about it. Legislation is passed, so there is no use puffing your chest out and getting all annoyed with the establishment. Secondly, super or premium unleaded will continue for a minimum of the next 5 years, so as long as you fill up with that everything stays the same. Thirdly the odd tank full will make no difference if you can’t find premium. Any issues that may occur are from long term use or storage.  However, there are a couple of issues with Ethanol, so let’s look at them one by one and see what you can do to mitigate any issues.


Ethanol is hygroscopic, which means that it attracts moisture from the atmosphere. The water separates in the fuel mix and then corrodes anything ferrious. This means the inside of steel fuel tanks, carb pots and steel fuel lines. The rust particles break off, get swirled around your fuel system and then block up in your fuel filter, carburettor or injection unit. It is a particular problem for classic cars, because we don’t use them all the time and therefore the fuel has more time to absorb water. The average classic does less than 1000 miles a year, which means that they use less than 50 gallons of fuel. The average modern car uses about 350 gallons a year which means the fuel inside is 7 times newer and has no time to absorb the water. Now this has been a problem for years, it is just going to get a little worse, so what can you do?

  • Keep you fuel fresh – Try to use the fuel you put in the car within two months
  • Install an inline filter at the tank and carburettor end to catch any debris
  • Change fuel filters every year as part of your regular maintenance
  • Don’t store the car with full tanks over the winter
  • Store your car in an environment with low humidity, around 45 to 60% is about perfect
  • There are fuel preservers on the market you can add to mitigate these issues when storing a car


The density and calorific value of E10 fuel will be different from E5. In the same way as you get a difference in performance running regular or super unleaded fuel there will be a difference between E5 and E10. If you are going to use E10 fuel all the time then you may well need to adjust the fuel/air ratio or the timing of the engine to suit. Your engine will probably run lean, but well within the parameters of being able to adjust the difference out. Our advice is that when you come in for a regular service, have whatever fuel you are most likely to use in the car. That way, when the mechanic tunes it up, he is doing so using the ‘right fuel’.

Ethanol Is Corrosive to Some Rubber Components

This is a fact, but we have had Ethanol in our fuel for donkey’s years, Europe have had E10 for a decade and the Americans have been using E85 since the 1960’s. So it is not a new phenomenon. Rubber hoses perish over time and are almost always overlooked when it comes to maintaining a classic. It is the same with tyres. 50% of all the vehicles we see in the workshop have 20 year old rock hard tyres, with perfect tread depth. They look OK, but are way more likely to fail and have because they flex less and crack as they move about or are put under pressure.

Rubber Fuel Line

There actually isn’t much rubber in any fuel system. Generally there is a flexible pipe from the fuel tank/pump to a ‘hard line’ that runs up to the engine bay, from there there are a few sections of rubber pipe that run from the hard line to the regulator and onto the carbs. If you can do it yourself, the new E10 approved flexible fuel line will cost less than 15 quid for 2 meters in any Auto Factors in the country and a couple of hours on a weekend. Alternatively, we can do this for you for about £150 + VAT

Rubber ‘O’ Rings

There are rubber ‘o’ or sealing rings in both carburettor and injection cars. They are way more likely to fail because they are 20 plus years old than simply down to another 5% of ethanol in the fuel. As part of your maintenance, keep an eye and nose on the fuel delivery components in your engine bay. If you can smell fuel, you have vapour present and therefore the beginnings of a leak. It needs to be tracked down and repaired. New old stock carb and injection kits should be avoided like the plague. The rubber is old, and although they might look OK are probably no better than the ones you are taking off.

Project Shop Rebuild Carbs and Injection Systems

We can strip and rebuild both carburettors and injection systems. We will not only make them safe, but doing so will also improve your performance and fuel consumption. Carburettor rebuilds start from £250. Get in contact for a quote.

What Our Customers Say

Project Shop rebuilt my Triumph TR6 chassis and body, which was an extensive job as it was a wreck. Several other workshops had looked at it and declined to take it on, but Simeon and his crew took a different viewpoint. I now have a car body and chassis, that although are 49-years old, the whole thing looks brand new. The attention to detail, and the efficiency with which the work was carried out, was outstanding. Highly recommended!


I took my brand new replica vintage car in to the Classis Project Shop for a tune of its carburetors as it wasn't running as well as it should. I was aware of some other niggling problems but took very little heed of them. A very detailed examination of the car was clearly carried out and there were a number of issues discovered. Some I was aware of and others I wasn't. What I got back was a car that was no longer 85% right - it was 100%. This gave me a huge amount of confidence in the reliability and safety of the car going forward. This company is extremely professional, with experienced and courteous staff and represents excellent value. I would certainly very highly recommend them.


I can’t recommend Project Shop highly enough and have used them multiple times in the past 4 years. Highly experienced classic car mechanics/engineers with a can do approach and encyclopaedic knowledge of how to repair/fix any problem – this is so critically important, is virtually impossible to find these days and saves time and most importantly money. Very reasonable hourly rates when you consider what you are getting and they seem to actually care about the car a great deal. All aspects of a project are discussed in detail before any actual work/repairs are commenced and the customer is kept regularly informed, the communication really is excellent. You are invited to visit and inspect the vehicle for yourself if an when an issue crops up and are made to feel most welcome not to mention the invaluable advice given on how to best maintain your vehicle moving forward. Without doubt one of the best classic car specialists in the country.


Owning a classic car is a combination of excitement, joy, pride and, mostly, frustration. The team at CPS share the first three and help to take the sting out of the fourth. Simeon is always available with good advice, sympathy and a willingness to go the extra mile to keep a car at it's best. His team look after the vehicle as of it is there own, and no detail is too minor.

A professional and detail orientated team, with extensive knowledge and experience, and a pleasure with which to deal.


A real delight to find people who love their cars. They have an encyclopaedic knowledge of the past and present issues surrounding the motor vehicle. A welcome change from the motor dealerships that don't care much about "old" only value "new" and think that they part of a car service industry whilst their only concerns are profits and sales targets.
From my own experience, Simeon and his team are a pleasure to deal with, since I was introduced to the Classic Project Shop my "Aston" has never run so well


Driving Puff yesterday was amazing - she felt like a new car again. Thanks to all the guys who have worked so hard to make this dream of mine a reality. And Puff thanks you too!


Did a fantastic job on my Goddess, running like a dream! Really enthusiastic bunch of people who know their stuff. The commitment and customer service is second to none and they will always be my first port of call from now on. Thank you.


Kind, reliable and so helpful. I had purchased my first T25 camper and they checked it over thoroughly, explaining everything to be done. Simeon was attentive and never made me feel out of place or awkward. Answered all questions and found the best solutions. Personal and caring service and excellent work, even helping me by phone when I was stuck in France with an oil leak! Superb people. Cannot praise their professionalism enough.


A great bunch of dedicated people who have a passion for cars.


Had a good look around whilst on a breakfast meeting and was very impressed. Well done.


Great bunch of lads and only too happy to help and offer advice.


I’ve not, in 52 years of motoring, had better service. Collection and delivery of my car, swift diagnosis and cure with excellent value for money. A group of very personable people who share my enthusiasm for motoring, I’ll use them again without a second thought. Thank you, Guys, I’ll be back!


The quality of the work and the people. Update! Been back again and just as happy. The team is talented and professional. They can have my Classic Mini next. 100% Recommended.


Driving Puff yesterday was amazing - she felt like a new car again. Thanks to all the guys who have worked so hard to make this dream of mine a reality. And Puff thanks you too!


Outstanding work carried out here, highly recommend.


Virtually replaced evety section of the inner bodywork of my Triumph TR6, and parts of the chassis. Didn't muck about, but just got on with it and did a great job. I will always go back there - every time. No question.


Good honest old fashioned values. Highly recommended.


Fantastic bunch of guys, very knowledgeable and professional.