Diesel fuel dilution level determination of diesel engine oil

A method for determining fuel dilution of diesel engine lubricating oil in a diesel engine. A first table contains a soot compensation factor (102-112), respectively, for each weight of oil selected among a predetermined range of oil weights. A second table contains fuel dilution levels (102'-112') for a plurality of predetermined compensated viscosity ratios. After determining the weight of the oil in the engine a first viscosity of the oil at a first temperature and a second viscosity of the oil at a second temperature are measured. Next, either a ratio (116) or a difference (714) of the first and second viscosities is determined. Using the ratio, soot in the oil is compensated using a soot compensation factor of the first table which is respective of the oil to thereby provide a compensated viscosity ratio (220). Finally, the compensated viscosity ratio is compared with the second table to thereby determine the fuel dilution level.