Method to determine the remaining useful life of automatic transmission fluid

A method of determining the remaining useful life of automatic transmission fluid used in an automatic transmission or automatic transaxle controlled by a programmable electronic controller, comprising the steps of:

• a. monitoring in-vehicle operation of a multiplicity of the same type of automatic transmissions or automatic transaxles as the first recited automatic transmission or automatic transaxle and collecting data on factors that bear on the useful life of automatic transmission fluid wherein one factor is time during electronic modulation of converter clutch (EMCC);
• b. deriving weighted constants for each factor based on the accumulated data;
• c. programming the programmable electronic controller to monitor the operation of the first recited automatic transmission or automatic transaxle and collect data on the factors that bear on the useful life of automatic transmission fluid including time during EMCC;
• and
• d. programming the programmable electronic controller to determine the remaining useful life of the automatic transmission fluid in the first recited automatic transmission or transaxle based on the collected data and weighted constants, including the collected data and weighted constant for time during EMCC factor.