1. What is E10 unleaded fuel?

E10 is a biofuel made up of 90% regular unleaded petrol and 10% ethanol. E10 fuel increases the share of renewable energies. 

  1. Why choose E10 unleaded fuel?

It is estimated that greener fuel could reduce CO2 emissions by 750,000 tonnes per year, the equivalent of taking up to 350,000 cars off the road. 

  1. What are the problems associated with E10 fuel in the fuel system?

There are three key areas when looking at the effects of E10 unleaded fuel: 

  • The engine’s ability to run and perform effectively 
  • Compatibility of the fuel system components 
  • The effects of corrosion, lacquers, varnish and gums which contaminate the fuel system components 
  1. Can all petrol cars run on E10 unleaded fuel?


  • Vehicles registered before 2002 are mainly not compatible and are recommended to use E5 higher octane super fuel. 
  • Some petrol vehicles up to 2011 are compatible; however, it is recommended to use E5 higher octane super fuel as compatibility is vehicle specific. 
  • Vehicles after 2011 are mainly compatible with E10 unleaded fuel. Still, we recommend you always check before use. Some manufacturers state that although the system is compatible, the use of E10 fuel may lead to drivability issues such as poor cold starting, poor performance, engine misfire or imbalance. 
  1. Why are the fuel system components not compatible with E10 fuel?

Over time, depending on driving styles, miles covered and refuelling habits, there is an increased degradation of E10 fuel. Fuel with 10% ethanol absorbs more moisture than lower ethanol content fuels. As degradation occurs, the fuel can become corrosive to some metals, rubber hoses, seals and fuel system components. 

  1. For engines where E10 is not recommended, is there a product that makes E10 fuel compatible?

No, you can only treat a vehicle to protect it from the effects of E10 unleaded fuel. 

  1. What types of vehicles are affected by corrosion?

  • Vehicles not compatible with E10 unleaded fuels can be more affected 
  • Low mileage vehicles without regular refilling of fresh fuel 
  • Vehicles that are stored for long periods of time 
  1. Can E10-compatible engines still have problems?

Yes, natural degradation of the fuel leads to corrosion, lacquers, gum and varnish formation. 

  1. How long does it take for E10 fuel to affect components?

It is widely accepted that natural fuel degradation can start to occur within 4-6 weeks. 

  1. What can accelerate natural degradation?

  • How much fuel is in the tank, and for how long. 
  • How often you fill-up 
  • Mileage/vehicle usage 
  • Fuel cap seal 
  1. How do I know if my vehicle is suffering from the effects of E10 fuel?

  • Poor operation and performance 
  • Difficult or poor starting 
  • P0300: random multiple misfire – a possible cause of injector fouling 
  • P0420: catalyst below efficiency – this can occur when the management system has made all the adjustments it can to maintain emissions, but they are still outside the parameters 
  • Component leaks 
  1. What can you do to reduce the effects of E10 fuel?

  • Fill the fuel tank regularly 
  • The more fuel in the tank, the less room for moisture to form. 
  • Treat the vehicle at every service to remove lacquers, varnish and gums and condition the fuel to reduce corrosion 
  1. How can I treat the symptoms of E10 unleaded fuel?

We recommend using Wynn’s Supremium Petrol to reduce the effects of E10 fuel, maintain vehicle performance, efficiency and responsiveness, and reduce component failure, while maintaining the environmental benefits of E10 unleaded fuel. 

  1. Is water the real problem with E10 fuel?

It takes E10 petrol three months or more than E0 petrol (without ethanol) to absorb enough moisture for phase separation to occur. 

By the time phase separation occurs in E10 petrol, the fuel is already stale, and engines can become difficult or impossible to start. The increase in lacquer formation contaminates fuel system components and can lead to poor running, misfires and emission-related fault codes. 

Ethanol fuel’s ability to absorb and retain water means it can become more corrosive and this over an extended period can cause damage to fuel system components. 

Many factors influence the amount of moisture that can enter the fuel tank: weather conditions, hot and cold days, the amount of fuel in the tank, how often you fill-up, mileage and the fuel cap seal are all factors that can influence the fuel. 

Some competitors present their product by putting petrol, water and some of their product in a test tube, shaking it and showing the customer that the product emulsifies or that the water is absorbed by the fuel. This is not relevant with E10 petrol, as the study shows that E10 petrol is already stale and there will be engine starting problems before the water and petrol separate (phase separation). 

  1. Does E10 fuel have an impact on fuel economy?

Ethanol fuel (E10) is less energy-dense than standard unleaded fuel. Therefore, fuel consumption can be affected. According to the RAC and the Energy Information Administration (EIA), the energy content of ethanol is around 33% lower than standard unleaded. The effect on fuel consumption is estimated at between 1-3%, with some motorists reporting a greater reduction in fuel consumption. 

In a consultation, one in four people said they were concerned about fuel economy. Ultimately, it was felt that fuel consumption depended on the driving style of the motorist, refinements of fuel blending by suppliers, and the cleanness of the vehicle’s fuel system. 

With E10 fuel being less energy-dense, a driver should not feel a difference in power because the ECU, the car’s computer, will change the air-fuel balance to make up for the loss.   

The engine management light may come on and an error code P0420 (catalyst efficiency below threshold) may be stored in the engine management circuit. This occurs when the engine management circuit has made the maximum possible settings. 

This problem may affect all vehicles using E10 fuel, not just those registered before 2011.