Abstract: A method of assessing oil condition in an engine includes receiving an engine variable including at least one of: a type of the engine, a displacement of the engine, a property of fuel used in the engine, and a property of oil used in the engine. The method further includes determining an operating parameter of the engine including at least one of an oil temperature, an oil pressure, a duty-cycle of the engine, a load on the engine, a speed of the engine, a power output of the engine, a rate of fuel consumption by the engine, and a time period elapsed since last change of oil in the engine. The method further includes calculating a rate of degradation of oil based on the determined engine variable and the determined operating parameter. The method further includes calculating a remaining service-life of the oil from the calculated rate of degradation.