Classic Car E10 Petrol: What Owners Need to Know
Written by Petro Olekhnovych, mobile mechanic in Aylesham, Kent
For most owners, the classic car E10 answer is simple: keep using E5 super unleaded. The Federation of British Historic Vehicle Clubs (FBHVC) recommends that all vehicles produced before 2000 use the E5 grade. One tank of E10 by mistake should not be a major problem, but it is not recommended for regular use.
What E10 petrol is and why it matters
E10 is petrol that contains up to 10% renewable ethanol. Standard 95 octane petrol became E10 in Great Britain in September 2021.
E5 is the “super” grade. It is 97 octane or higher and contains no more than 5% ethanol. GOV.UK says E5 is available at most filling stations and will remain available.
One thing to watch in rural Kent: GOV.UK notes that some rural, remote or very small filling stations may only sell one grade. If you are heading out on a long run, it is worth knowing where your E5 stops are.
Is your classic car compatible with E10?
GOV.UK says all new cars made since 2011 can use E10. Most cars made since the late 1990s are approved for it too, but some models from the early 2000s are not.
Older cars are a different story. GOV.UK says classic, cherished and older vehicles may not be compatible, and many classic manufacturers are missing from the official E10 checker. If your car is not listed, the government advice is to keep using E5 and ask your owners’ club or a garage.
The FBHVC goes further. It recommends E5 for every vehicle produced before 2000, plus some early 2000s cars that are not E10 compatible.
Classic car needs some care?
Servicing, recommissioning and mechanical restoration for older cars across Kent.
WhatsApp for a free quote Call 07563 350335
Labour £30 to £50 per hour depending on the job. Send your reg number and we will reply with a price before any work starts.
What ethanol can do to an old fuel system
The FBHVC lists three main risks for historic vehicles:
- Corrosion and tarnishing of metal parts in the fuel system.
- Damage to rubber and other seal materials (it calls these elastomers).
- A leaner fuel mixture, which can mean less power or the engine running hotter.
Some older cars used fuel system materials that ethanol can damage. The FBHVC names cork, shellac, epoxy resins, nylon, polyurethane and glass-fibre reinforced polyesters.
It also warns about a few specific problems:
- Old or tired hoses may fail quickly, causing leaks or fuel “sweating” through the lines.
- Some fuel tank repair coatings can break down and clog the fuel system.
- Plastic carburettor floats can be affected, which may cause flooding and leaks.
- Ethanol can loosen old deposits in the tank and lines, which can then block filters.
Safety first: if you can smell petrol or see fuel leaking or weeping from a hose, stop using the car. A petrol leak near a hot engine is a fire risk. Get the fuel system checked before you drive it again.
I put E10 in my classic by mistake. What now?
Do not panic. GOV.UK says one tank of E10 in a car that is not compatible should not be a major problem. You do not need to drain the tank. Fill up with E5 at your next stop.
The FBHVC adds one important point: do not leave the car stored for a long time with E10 in the tank. Use it up and top up with E5 before you park the car for a while.
Storing a classic car over winter
Fuel sitting in a car for months matters more on a classic. The FBHVC advice for vehicles laid up for a long time is to use ethanol-free petrol, which some suppliers sell.
It also says not to leave the fuel system dry. A dry system can lead to corrosion and cracking of seals and gaskets. Our guide to laying up a classic car for winter covers the rest of the storage checklist.
Do fuel additives help?
Partly. The FBHVC says corrosion inhibitor additives can be very effective at controlling ethanol corrosion. It recommends adding one to both E5 and E10 as an extra precaution.
But it also says it is not aware of any additive that gives complete protection to seals and gaskets. An additive is not a substitute for checking the fuel system.
Note that the FBHVC also points out some E5 super grades contain no ethanol at all. This varies by fuel brand and location, so check with the station if it matters to you.
Can a classic be made to run on E10?
The FBHVC suggests a few steps if you plan to use E10:
- Replace seal and gasket materials with ethanol-compatible versions first.
- Inspect and renew hoses, seals and gaskets as part of routine maintenance.
- Check metal parts such as tanks, lines and carburettors for corrosion.
- Consider enriching the fuel mixture, because ethanol leans it out.
Every car is different, so ask your owners’ club what works for your model. If the mixture needs adjusting, our post on carburettor tuning explains what is involved.
How we can help
We are a mobile mechanic based in Aylesham, and we come to your home or workplace. We cover Canterbury, Dover, Deal, Sandwich, Folkestone and the villages in between. See the full list on our areas we cover page.
Classic and vintage car servicing and repair is a big part of what we do. We can inspect your fuel system for leaks, weeping hoses and corrosion, and change fuel filters on petrol cars. If your car has been off the road for a long time, we also offer recommissioning.
Labour is £30-£50 per hour depending on the job and its difficulty. Parts are extra. We agree the price with you on WhatsApp before any work starts.
Frequently asked questions
Can I use E10 in my classic car?
The FBHVC recommends E5 for all vehicles produced before 2000. GOV.UK says owners of classic cars not listed in the E10 checker should keep using E5.
Will one tank of E10 damage my engine?
GOV.UK says a single tank should not cause engine damage and you do not need to drain it. Fill with E5 next time.
Is E5 petrol being withdrawn?
GOV.UK says E5 will remain available. It does not give an end date.
Should I use a fuel additive?
The FBHVC recommends a corrosion inhibitor as an extra precaution, but says no additive it knows of fully protects seals and gaskets.
Need help? Send a WhatsApp to 07563 350335 with your car’s make and model and we’ll come to you.
Classic car needs some care?
Message us on WhatsApp with your reg and postcode for a price before any work starts.
WhatsApp for a free quote Call 07563 350335
Labour £30 to £50 per hour depending on the job. Send your reg number and we will reply with a price before any work starts.
