E10 Petrol Problems: Is Your Car Struggling?

The Ethanol Shift

In September 2021, the UK Government mandated that all standard 95-octane unleaded petrol switch from an E5 blend to an E10 blend. This means standard petrol now contains up to 10% renewable ethanol. While this reduces the UK's overall CO2 emissions, it introduced a host of mechanical issues for drivers of older vehicles.

Why is Ethanol Bad for Old Cars?

Ethanol has two distinct chemical properties that make it hostile to older engines:

• It is a solvent: Ethanol aggressively eats away at older rubber fuel lines, plastic seals, and fiberglass fuel tanks. Over time, these components become brittle and crack, leading to dangerous fuel leaks.
• It is hygroscopic: Ethanol absorbs moisture from the air. If E10 fuel sits in a car's tank for a few weeks without being used, the water and ethanol separate from the petrol and sink to the bottom of the tank, causing internal rusting and severe engine misfires.

Is My Car Safe?

If your car was built after 2011, it is 100% compatible with E10. If it was built between 2001 and 2011, it is highly likely to be safe, but you should check the government's official E10 compatibility checker.

What to do if your car isn't compatible

If you drive a classic car, a modern classic, or a vehicle explicitly not rated for E10, you must avoid the standard green pumps. Your only option is to purchase "Super Unleaded" (Premium 97+ Octane), as this remains blended at the older E5 standard. Because premium fuel is highly expensive, it is vital to use an aggregator like FindPetrol to track down the cheapest E5 prices in your local area to soften the financial blow.

Local prices differ far more than most drivers expect. For a worked example, see current petrol prices in Birmingham.

Comparing petrol prices before you fill up

Whichever grade you choose, the forecourt matters more than the badge. Standard unleaded currently runs from 142.9p to well above the 161.4p national average depending on where you stop. Check petrol prices near me by postcode, or see the full picture on our UK fuel prices page before you commit to a tank.