Patent ID: 8746046

Claim:
A method for a estimation of oil viscosity in an internal combustion engine, the internal combustion engine subjected to fuel post injections to activate a regeneration process of a particulate filter and to a fuel hydrocarbon evaporation events affecting oil viscosity, comprising: determining if the particulate filter is subjected to the regeneration process, and if the particulate filter is subjected to the regeneration process: calculating an oil viscosity decrease during the regeneration process as a function of an oil dilution rate; and calculating an oil viscosity increase after the regeneration process as a function of an hydrocarbon evaporation rate and of a time during which fuel hydrocarbon evaporation takes place, wherein the time is a function of time spent evaporating one or more kinds of fuel hydrocarbons from engine oil in a previous fuel hydrocarbon evaporation event; and wherein a different hydrocarbon evaporation rate is set for each kind of fuel hydrocarbon following a regeneration process based upon a specific mission profile of the internal combustion engine.