Abstract: Projektet syftar till att minska bränsleförbrukningen i fordon genom att minska förlusterna i växellådan genom att förbättra smörjmedlets egenskaper. Smörjmedlets olika komponenters bidrag till förluster kommer att undersökas med målet att optimera sammansättningen för att minimera förluster, förlänga bytesintervallet samt bibehålla maskindelarnas livslängd.Abstract: In view of growing concerns towards energy conservation and environmental problems, vehicle manufacturers today face increasing demands to produce fuel efficient vehicles. In view of these concerns, the reduction of losses through tribological measures is the major challenge facing the vehicle industry. This project aims to increase the fundamental knowledge about the tribological systems that are found in gear transmissions. Very little research work has to date been performed in this area so the potential for improvements is great. The goal with the project is to reduce the total environmental impact resulting from gear transmissions. This can be achieved through an increased understanding of the interaction between base-fluid and additives during oil-film formation in the transmission. By developing methods that minimise the losses and maximise the service life of the lubricant the total environmental impact can be reduced.