The cost of maintaining aeroplanes is still considerable. It concerns especially operation cost where fuel is a substantial part. At the moment the special 100LL gasoline is used to fuel aircraft piston engines. It is about 20% more expensive than ES95 gasoline featuring comparable properties. The article shows the results of test-bed research conducted on the radial piston aircraft engine fuelled by aircraft 100LL gasoline and automotive ES95 gasoline. The object of research was ASz-62IR engine by WSK PZL-Kalisz that was equipped with an experimental fuel injection system. Power, fuel consumption, head temperatures and indicated pressure in cylinders were analysed in the selected typical operating points. The testing was carried out in steady state. It was proved that it is possible to exchange fuels with no engine power loss and merely an insignificant increase of fuel consumption but with significant increase of IMEP cycle-to-cycle variation. (C) 2010 Elsevier Ltd. All rights reserved.