The article presents the structure and a principle of operation of a simple indicator of the type of a fuel-air mixture supplying a spark-ignition engine with a direct fuel injection. The designed indicator was tested, as a result of which its correct operation was verified. By using information from the indicator, it was possible to assess its usefulness for assisting the driver in an economical driving style. Preliminary studies show that thanks to the use of the developed indicator, it is possible to save about 10% of fuel as a result of the correction of the economic driving style on the route selected for the purpose of this research paper. The target of this study was to confirm a noticeable reduction in fuel consumption when supplying the engine with a stratified mixture. In order to obtain more accurate data, the research should be extended to include a greater number of routes and its division into urban and non-urban areas.