Automatic engine oil change indicator system

In a motor vehicle having an engine containing lubricating oil which has a useful life that varies in accordance with engine operating conditions, a method for advising the operator of the vehicle of the need to change the oil, such method comprising the steps of:

• periodically computing an effective usage amount in relation to the product of actual engine revolutions and a penalty factor which operates to increase the effective usage amount when the engine operating conditions tend to cause increased degradation of the engine oil, the penalty factor being determined as a sole function of the engine oil temperature as it relates to empirically determined data without regard to the engine load;
• and
• accumulating said periodically computed effective usage amounts, and actuating an indicator for advising the operator that the engine oil should be changed when such accumulated usage amount reaches a predetermined value indicative that the useful life of the engine oil has been substantially attained.