Mogas contamination in Freiburg im Breisgau

On August 29, the mogas tank at Freiburg airfield in southern Germany was contaminated by a batch of fuel that had already been mixed in the tanker. Swiss pilots could also be affected. 

This went unnoticed for several weeks until a laboratory discovered that the mogas contained around five percent diesel. A maximum of 0.5 percent would be permitted. Up to and including October 21, the Mogas filling station, where many Swiss pilots also fill up near the border, was operating with the contaminated fuel.

It won't be that bad, some people will think, the diesel probably burns in the air too. It's not that simple, as many affected owners of aircraft have now found out. Mogas must never be mixed with diesel. Otherwise, the worst case scenario could even be engine failure.

The problem: diesel in mogas lowers the octane rating. According to a statement from the German Aeroclub DAeC, every percentage of diesel reduces the octane rating by 0.7 points. If the mogas originally has 98 octane, only 94.5 octane remains with five percent diesel. However, if an engine needs the full 98 octane to operate, it can be damaged or even fail completely if it only has 94.5 octane left, according to the DAeC, due to so-called knocking, an uncontrolled self-combustion of the air-fuel mixture.

Swiss pilots who filled up with Mogas in Freiburg, Baden-Württemberg, between August 29 and October 21 and who may not have been contacted by the airfield due to cash payment of the fuel should contact Freiburg Airfield.

In any case, the public liability insurance of the tank filler at Freiburg Airport is now facing financial claims of a not inconsiderable amount from several dozen affected aircraft owners for the unscheduled maintenance work. Jürgen Schelling