The UK’s adoption of E10 fuel has been widespread, with nearly every gas station across the country now dispensing it from the green pump. In September 2021, the government announced that E10, an enhanced ethanol-mix fuel, would become the new standard grade of unleaded petrol in Great Britain. Northern Ireland followed suit in November 2022. The decision to introduce E10 was based on its lower CO2 emissions compared to the previous E5 blend. Ethanol, which is made from a range of plants, absorbs CO2 during its production, partially offsetting greenhouse gas emissions. The introduction of E10 marked a doubling of the amount of ethanol used in petrol to 10%, with the UK government estimating that it could reduce CO2 output by 2%.
Most cars built in the past 20 years should be able to run on E10 fuel, as it has been widely available in other countries for years. Only a small percentage of vehicles, around 634,000 out of approximately 30 million in the UK, may not be compatible with E10. The majority of these incompatible cars are classic or vintage models, with only 150,000 of them being built after 2000. Older cars may experience issues with the increased ethanol content, such as blocked fuel filters, damaged fuel pumps, fuel line degradation, and corroded carburettors. However, owners of these cars can still purchase E5 fuel in the form of higher-octane super-unleaded, although at a higher cost.
For cars that are compatible with E10, there should be no significant difference in performance compared to using E5 fuel, apart from a slight drop in fuel economy. If your car’s user manual states that it can run on E10, there is no reason not to use it. However, if your car is not compatible with E10, E5 fuel is still available, albeit in a more expensive form. To determine whether your car can run on E10, you can check the government’s E10 compatibility checker on their website or consult your car’s manual or manufacturer.
Using E10 fuel in an incompatible car may lead to long-term issues with rubber and plastic components, but one-off use should not cause any immediate problems. If you mistakenly fill an incompatible car with E10, it is recommended to top it up with E5 fuel after using a quarter of the tank. As long as you do not regularly use E10 in an incompatible car, you should not encounter any major issues. If you plan to store an incompatible car for an extended period, it is advisable to clear as much E10 from its fuel system as possible.
When it comes to performance cars, such as the BMW M5, Mercedes-AMG A45, and Porsche 911, which are designed to run on high-octane fuels, it is still recommended to use super-unleaded fuels with octane ratings of 98 RON or better. While these high-octane fuels are currently E5 blends, running these cars on E10 may result in a slight change in power delivery. Many studies have shown that higher-octane fuels can provide modest power gains and improved performance on the road. Although super-unleaded is more expensive, the slight increase in fuel efficiency over E10 may offset the cost difference.
In terms of fuel economy, E10 may reduce fuel efficiency by around 3-4% compared to fuel without any ethanol. This is because ethanol has around 33% less energy than pure petrol, requiring more fuel to achieve the same power output. However, if your car’s manual states that it is compatible with E10, there should only be a minimal difference in fuel economy compared to using E5 fuel.
It is safe to mix E5 and E10 petrol without any immediate issues with engine performance. The risk of using E10 in an incompatible car lies in the corrosion of rubber and plastic components over an extended period of time. If you accidentally fill an incompatible car with E10, it is recommended to top it up with E5 fuel after using a quarter of the tank. However, regularly using E10 in a car that does not support its use may lead to long-term damage.
Overall, E10 fuel has been widely adopted in the UK, with most cars built in the past 20 years being compatible with it. For incompatible cars, E5 fuel is still available but at a higher cost. Using E10 in an incompatible car may have long-term effects on rubber and plastic components, but one-off use should not cause immediate issues. Performance cars designed for high-octane fuels may still benefit from using super-unleaded, although running them on E10 should not cause major problems. While E10 may result in a slight drop in fuel economy compared to E5, the difference should be minimal for compatible cars. Mixing E5 and E10 petrol is safe as long as it is not done regularly in an incompatible car.
