Conversion of automobiles to different type of fuel involves evaluation of material compatibility of the new fuel and components of the engine and fuel supply system. Automobiles, equipped with a spark ignition gasoline fueled engine, can be converted to work on gaseous fuels, such as liquefied petrol gas or liquid fuels, such as ethanol/gasoline blend E85. In case of such conversion, materials in question can be divided in two categories - metallic and polymeric. This study focuses on evaluation of compatibility of the fuel supply system parts made of non-elastomer polymeric and fuel containing up to 85 % of ethanol. Automobile parts which are made of polymeric materials have standardized code markings, required for recycling purposes. The authors propose to use the material code markings to identify the type of polymeric material of the fuel supply system parts. Typical material choice for the main fuel supply system parts is presented and its compatibility with E85 fuel discussed.