On-vehicle evaluation of oil formulation

A method of identifying a replenishing oil when a first volume of replenishing oil is mixed with a second volume of used oil to create a volume of mixed oil, comprising:

• measuring the electrical resistivity of the used oil;
• measuring the second volume;
• determining the first volume;
• measuring the electrical resistivity of the oil mixture;
• using an appropriate mixture rule and knowledge of the first and second volumes to compute the resistivity of the first oil;
• and
• comparing the resistivity of the replenishing oil with known resistivities of candidate replenishing oils until a candidate oil with a resistivity suitably correspondent with the resistivity of the replenishing oil is identified.

A method of identifying a first unused oil present in an oil mixture comprising a first volume of a first unused oil and a second volume of a second used oil comprising;

• storing data on oil resistivity for some number of reference unused oils in a retrievable manner;
• measuring the electrical resistivity of the second oil;
• measuring the second volume;
• determining the first volume;
• measuring the electrical resistivity of the oil mixture;
• using an appropriate mixture rule and knowledge of the first and second volumes to compute the resistivity of the first oil and;
• identifying the first unused oil through substantially matching the resistivity of the first oil with the resistivity of a one of the reference unused oils.

A method of identifying a first unused oil present in an oil mixture in an engine generated by addition of a first volume of a first unused oil and a second volume of a second oil comprising;

• storing data, in a retrievable manner, on the variation of oil resistivity with engine operating time, measured under specified engine operating conditions, during use in an operating engine for some number of reference oils;
• measuring the variation of electrical resistivity of the second oil with engine operating time and extracting the engine operating time corresponding to the time, tMax at which the variation of resistivity with engine operating time exhibits a maximum;
• measuring the second volume of the second oil;
• determining the first volume of the first oil;
• recording the engine operating time at which the first volume is added to the second volume as a reference time;
• repeatedly measuring, under specified engine operating conditions, the variation of the electrical resistivity of the oil mixture with engine operating time, during use in an operating engine where the time is measured from the reference time with sufficient frequency to generate a near-continuous record of resistivity with engine operating time;
• extracting from the near-continuous record of resistivity with engine operating time a time interval tMax* from the reference time at which the resistivity of the oil mixture exhibits a maximum;
• attributing the time tMax* at which the oil mixture exhibits a peak in its resistivity with engine operating time to the first unused oil and;
• through substantially matching the time tMax* with the time to peak resistivity of one of the reference unused oils and identifying the first unused oil with the one of the reference unused oils.

A method of identifying a first unused oil present in an oil mixture in an engine generated by addition of a first volume of a first unused oil and a second volume of a second oil comprising;

• storing data, in a retrievable manner, on the variation of oil resistivity with engine crankshaft revolutions, measured under specified engine operating conditions, during use in an operating engine for some number of reference oils;
• measuring the variation of electrical resistivity of the second oil with engine crankshaft revolutions and extracting the engine operating time corresponding to the count, rMax at which the variation of resistivity with engine crankshaft revolutions exhibits a maximum;
• measuring the second volume of the second oil;
• determining the first volume of the first oil;
• recording the engine crankshaft revolutions at which the first volume is added to the second volume as a reference crankshaft revolution count;
• repeatedly measuring, under specified engine operating conditions, the variation of the electrical resistivity of the oil mixture with engine crankshaft revolutions, during use in an operating engine where the time is measured from the reference time with sufficient frequency to generate a near-continuous record of resistivity with engine crankshaft revolutions;
• extracting from the near-continuous record of resistivity with engine crankshaft revolutions a count rMax* from the reference crankshaft revolution count at which the resistivity of the oil mixture exhibits a maximum;
• attributing the value rMax* at which the oil mixture exhibits a peak in its resistivity with engine crankshaft revolutions to the first unused oil and;
• through substantially matching the engine crankshaft revolutions rMax* with the engine crankshaft revolutions to peak resistivity of one of the reference unused oils and identifying the first unused oil with the one of the reference unused oils.