The role of MoDTC tribochemistry in engine tribology performance. A Raman microscopy investigation

In order to tackle the new challenges towards the reduction of carbon emissions in transport industry, the present work aims to understand the effect of the friction modifier (FM) molybdenum dithiocarbamate (MoDTC) on the performance of an automobile engine. A petrol engine has undergone motored test trials, measuring the friction torque reduction when the FM additive is blended into a fully formulated SAE 5W30 oil. Moreover, the engine has been dismantled after the test, investigating the tribochemistry of MoDTC at different key engine components undergoing boundary lubrication, using Raman microscopy. This work demonstrates that materials and contact pressure play a crucial role in MoDTC tribochemistry to form a low friction tribofilm, contributing to global engine friction reduction. •The addition of 1% MoDTC additive to a fully formulated engine oil delivered a maximum friction torque reduction of 2.5%.•MoS2 was found in engine areas where boundary lubrication regime was met.•No MoS2 was found in non-ferrous surfaces.•Piston rings underwent measurable wear during motored tests, leading to coating removal.