The aim of this thesis is to investigate the application of a small Wankel rotary engine (Rotron RT300, 300 cm3) as range extender, studying which are its main limits, understanding which aspects can be modified or optimized in order to understand if it is worth to use an engine with limited automotive diffusion for such an application. The small number of production cars using this engine is due to the fact that Wankel has several problems linked to fuel consumption, oil consumption and pollutant emissions. Part of these problems are strictly connected to the lubrication system: this project focuses on the study of the main components that are lubricated, to understand how and if it is possible to substitute the lubricant oil in order to reduce the friction losses and the seals wear, and to find out which is the best one in term of pollutant formation and emission according to the current regulations.