Patent Document ID: 4847768
Application ID: 07237762
Patent Flag: 1

Claim One:
1. In a motor vehicle having an engine containing lubricating engine oil which has a useful life that varies in accordance with engine operating conditions and apparatus for determining the remaining useful life of the engine oil in engine operation from the engine oil temperature, apparatus for determining the engine oil temperature without direct measurement thereof comprising, in combination: means for storing a datum having a first value indicating that the engine oil temperature is in a warming range and a second value indicating that the engine oil temperature is in an equilibrium range, the stored datum being set to the first value at the beginning of engine operation; means responsive to the first value of the stored datum to calculate the engine oil temperature T.sub.o according to a warmup equation T.sub.o =k.sub.1 +k.sub.2 T.sub.r +k.sub.3 F.sub.f, wherein T.sub.r is a reference temperature indicative of engine oil temperature at the beginning of engine operation, F.sub.f is a firing factor proportional to the number of combustion firings since the beginning of engine operation, and k.sub.1, k.sub.2 and k.sub.3 are constants; means responsive to the second value of the stored datum to calculate the engine oil temperature T.sub.o according to an equilibrium equation T.sub.o =k.sub.4 +k.sub.5 T.sub.e +k.sub.6 S.sub.e, wherein T.sub.e is an engine temperature indicative of engine oil temperature, S.sub.e is engine rotational speed, and k.sub.4, k.sub.5 and k.sub.6 are constants; means for storing the calculated engine oil temperature T.sub.o for use by the apparatus for determining the remaining useful life of the engine oil; and means for setting the stored datum to its second value when the calculated engine oil temperature T.sub.o exceeds a predetermined warmup temperature.