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On-line measurement of oil dilution is of particular interest in light of new environmental regulations imposed on today's high-performance engines. In particular, after-treatment devices such as diesel particle filters (DPF) need to be periodically re-generated in order to eliminate their soot content. Such re-generation process is usually performed by using post-injection cycles that can induce a transfer of fuel to the lubricant, resulting in oil dilution. A new method was recently developed by DSi sprl and Total France for monitoring oil dilution on running engines. It is based on lubricant labelling using a new radiotracer compound, which is stable and representative of the oil distillation interval. Measurements are performed by circulating the engine oil to a measuring chamber where dilution is monitored. The method was recently applied to gasoline and diesel engines where dilution results have proven to be accurate and repeatable.

Thin Layer Activation (TLA), a radionuclide technique, was recently applied at the Research Center of ELF Solaize, France, to perform on-line monitoring of wear on diesel car engines. Measurements aimed at better understanding how wear develops on cam lobes as a function of various parameters such as lubricant formulation, soot concentration, and oil aging. The engine itself (passenger car diesel engine) was operated under severe steady state conditions (speed, torque, oil temperature and smoke) and on-line measurements were performed by applying two independent methods: direct measurement of material loss from cam lobes (inlet and exhaust valves) and concentration measurement of worn debris in oil or in the oil filter. These methods have proved to be very repeatable and absolute wear values given by TLA were consistent with those measured by profilometry.