Patent ID: 8050814

Claim:
A method for determining the remaining useful life of oil in a transmission having a torque converter with a lockup clutch, the method comprising: detecting if the transmission has completed a new shift; determining a total shift count if said new shift has been completed; determining an accumulated time parameter; determining an accumulated distance parameter; determining a transmission temperature degradation factor based at least in part upon the accumulated time parameter; determining a total degradation factor based at least in part upon said transmission temperature degradation factor; determining an oil life time limit based at least in part upon said total degradation factor; the total shift count, and the accumulated time parameter determining if said accumulated time parameter is greater than said oil life time limit; determining an oil life distance limit based at least in part upon said total degradation factor; the total shift count, and the accumulated distance parameter determining if said accumulated distance parameter is greater than said oil life distance limit; and activating a service indicator configured to signal that transmission oil service is required in response to at least one of said accumulated time parameter being greater than said oil life time limit and said accumulated distance parameter being greater than said oil life distance limit.