Ethanol (ENG)

Let’s be clear. Only FFV-vehicles (Flexible Fuel Vehicles) can run on Bio-Ethanol. Bio-ethanol being 15% standard gasoline with 85% Ethanol.  So, this is not for our Royal Enfield engines. This type of fuel is only available in Brazil, Sweden and USA.

In Europe, the gasoline contains not more then 5% ethanol (spec EN 228). However, Europe wasn’t Europe if there were no exceptions. Finland, France and Germany have a 10 % ethanol mixture in the service stations.

The indication is as follows:

  • E5 is 5 % bio-ethanol is blended into the standard gasoline.
  • E10 is 10 % bio-ethanol is blended into the standard gasoline.


Ethanol contains less energy compared to gasoline. For an E10 fuel, this is 2% less compared to conventional gasoline. Meaning an extra consumption of 1,5% for the same performance (source: Allgemeine Deutsche Automobil-Club).

Ethanol dangerous for your engine?

If high pressure and high temperatures occur, ethanol can provoke corrosion on aluminum parts. This can be the case in the fuel conduits, fuel pump,…

Ethanol can also affect certain plastics and rubbers. Hoses, gaskets and plastic gasoline tanks (single-layer) might show a creeping leakage. In most cases this is discovered by an increasing gasoline smell.


  • For the new Royal Enfield engines there is no immediate problem. The concept of the European engine supports the use ofethanol blended (limited) gasoline. To play on the safe side: use an E5 blend.
  • For the old Royal Enfield it is best to take gasoline without ethanol or at most an E5 grade. In Sweden and France, this might be a problem to find. In Germany, service stations sell an E5 next to the E10 gasoline. Eventual you can exchange rubbers and plastic materials in the fuel system by newer materials.

If the inside of an old gasoline tank is sealed with a resin, ethanol can affect this resin. So , beware of those “resin”-tricks. They avoid an immediate cost for a new tank, but there is a potential risk in it.


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