Method and device for monitoring the dilution of the lubricating oil by the fuel in an internal combustion engine

The invention relates to a method of determining the rate of dilution of the lubricating oil by the fuel in an internal combustion engine. The invention is characterized in that it comprises the following steps consisting in: marking either the lubricating oil or the fuel with a radioactive tracer, measuring the radioactivity of an oil sample using a detector that is sensitive to the radioactive radiation emitted by the radioactive tracer, and transmitting the results of the aforementioned measurements to a computer which uses said results in order to calculate the rate of dilution of the lubricating oil by the fuel. The invention also relates to a device which is used to implement said method, in particular a test bench for engines.