Why Bother With E10 Fuel? Surely E5 Is Enough?

Why Bother With E10 Fuel? Surely E5 Is Enough?
As a classic car owner, chances are you’ve already had your fair share of pub chats, forum debates, and petrol station head-scratching over E10 fuel. Ever since the UK rolled out E10 petrol as the standard at the pumps in 2021, the classic car community has been buzzing with one key question: “Why bother with E10? Isn’t E5 good enough?”

The short answer? Yes, E5 is still a go-to option for many classics - but understanding E10, and knowing why it exists, could save you a lot of trouble (and money) down the line.

What’s the difference between E5 and E10?

Let’s start with the basics. The “E” in E5 and E10 stands for ethanol - a biofuel typically made from plant materials. E5 contains up to 5% ethanol; E10 doubles that to 10%.

In September 2021, the UK government introduced E10 petrol as the new standard unleaded at forecourts across England, Scotland, and Wales (Northern Ireland followed in 2022). The change was driven by environmental goals: increasing ethanol content helps reduce CO₂ emissions from petrol vehicles by up to 750,000 tonnes per year, which is equivalent to taking 350,000 cars off the road.

So far, so green. But for classic vehicle owners, the arrival of E10 hasn’t exactly been cause for celebration.

While modern engines are designed to handle higher ethanol content without issue, many classic engines are not. Ethanol is hygroscopic, which means it absorbs water from the atmosphere. This can lead to condensation in the fuel system, which in turn causes corrosion - especially in older components like carburettors, fuel tanks, and rubber hoses.

It’s not just corrosion that’s a concern. Ethanol also acts as a solvent, which can dissolve old varnishes and deposits inside fuel systems. In modern cars, that’s no big deal. In older engines, it can clog fuel lines, filters, and carbs, causing poor running - or worse, breakdowns.

Here are some real concerns classic owners should be aware of:

• Perished fuel lines and seals: ethanol can degrade rubber and plastic components not designed for it.
• Blocked jets and filters: ethanol's solvent properties can dislodge gunk that’s been stable for years.
• Poor starting and running: ethanol affects air/fuel mixtures and volatility, which can disrupt performance in carburetted engines.

According to the Federation of British Historic Vehicle Clubs (FBHVC), around 600,000 vehicles on UK roads are not compatible with E10 - a large proportion of which are classics.

Thankfully, E5 hasn’t disappeared, yet. While E10 is now the standard ‘Premium’ (95 RON) petrol, E5 remains available as the higher-octane ‘Super Unleaded’ (97+ RON) at most forecourts.

But here’s the catch: E5’s availability isn’t guaranteed forever. The UK government has only committed to keeping E5 on sale in the Super grade for the “foreseeable future,” but there’s no long-term legal requirement. And, as fewer modern cars need it, some rural or smaller stations may eventually stop stocking it.

In short: E5 is safe, but it’s not a certainty. And that’s why understanding E10 - rather than avoiding it entirely - is worth the effort.

Can classic cars run on E10?

With care, yes. Not all classics are automatically incompatible with E10. Many cars from the late 1980s onward (especially fuel-injected models) can handle E10 with minor adjustments - such as fuel hose upgrades or adding corrosion inhibitors.

Here’s what classic owners can do to minimise the risks:

• Upgrade fuel system components: replace old rubber hoses and seals with ethanol-resistant alternatives (look for R9 spec fuel hose).
• Use additives: ethanol protection additives can help combat corrosion and moisture issues.
• Don’t store E10 fuel long-term: it degrades faster than E5, especially in tanks that aren’t sealed.
• Check compatibility: use the government’s online E10 compatibility checker (though it mainly covers newer vehicles).

If your classic is used regularly and you’re proactive about maintenance, E10 might not be as scary as it sounds.

The move toward biofuels isn’t going away. As the UK pushes toward its Net Zero 2050 targets, fuels like E10 will continue to evolve - and may be joined by even greener alternatives, like synthetic fuels or E85, in time.

For classic owners, this doesn’t mean the end of the road. In fact, it’s a chance to adapt, prepare, and keep enjoying your car - without being left behind by fuel changes.

Groups like the FBHVC are working hard to represent historic vehicles in fuel policy conversations, ensuring we’re not forgotten. And, as long as there’s a strong classic community (which there is), there will be demand for compatible fuels and solutions.

So, is E5 enough for now? Probably. But ignoring E10 entirely is a risky move - especially if you rely on a favourite forecourt that could one day phase E5 out. By understanding how ethanol works, upgrading key parts, and using additives where needed, classic owners can protect their pride and joy while still embracing a fuel future that’s here to stay.