Flex Fuel

E85 is a different type of fuel used for internal combustion engines. E85 is a blend of gasoline and ethanol. Generally the mixture is about 85% ethanol and 15% gasoline. The mixture may vary because of the climate of your country or time of the year. In colder climates you will have less e85 to assure a better cold start and running temperatures. 

The ethanol used in E85 is an alcohol-based fuel made by fermenting and distilling crops, corn mostly. Vehicles that have the ability to take E85 are advertised as Flex Fuel vehicles. This means that your vehicle can take anything between 0% ethanol (or 100% gasoline) and 100% ethanol (or 0% gasoline).


  • Less emissions
  • More power/torque
  • Doesn't heat engine up as much as gasoline
  • Cheaper than gasoline (in some countries)
  • Less tax (in some countries)
  • At 500 gas stations in France


  • 20% more fuel consumption
  • Not available in every country
  • More corrosive than gasoline
  • Wears out injectors faster if not upgraded
  • Difficult cold starts in cold climates

How it works

There are two different methods to enable your vehicle for Flex Fuel. The first one is using a piggyback system with an ethanol sensor. The system we use is from the Finnish brand eFlexfuel. This control unit will read how much ethanol content there is in the tank. With this information it will decide when to open the injectors for the right amount of fuel and the right timing. The advantages of this system are that it is easy to install yourself and gives you a lot of data on your phone via an app. You will also never have to worry about the E85 tune being removed by your dealership when bringing in your vehicle for service. The drawback is that this system only works with port injected engines, is more expensive and enables flex fuel by tricking the ECU rather than optimising it.

The second method is remapping the ECU and our preferred method. In order for the vehicle to run on E85 when remapping, we have to develop our own engine mappings. In order to control the injection and timing, we use the information from the O2 sensors. The big advantage with ECU mapping is that we can control a lot more parameters than with a piggyback system. The drawback of this system is that if the manufacturer does an update on the ECU when it's in for servicing, the vehicle will not be able to run on E85 anymore.


Because ethanol has a high horse power gain, ethanol and some variants are often used in motorsports. Currently ethanol is used in the NASCAR series and Indy car racing series. Often ethanol is also used in drag racing. To have good power using ethanol you need high compression. This is why usually the internals are upgraded. This is a service that we offer as well.