Questions and Answers

Transmission Service Intervals Q. Hello: I have a 1999 Ford Taurus LX (Vulcan V-6, Transmission AX4S). Question, quite simply is: Do I need to change the transmission fluid every 30,000 miles as indicated in the maintenance schedule? The reason I am asking is that (1) the schedule is for ALL Ford cars and trucks, not just the Taurus and (2) the fluid is MERCON V, which I thought is long life.

I did change it already at 35,000, but feel that since I do all highway that every 30,000 is overkill.

Thank you!

A. Service intervals depend on the conditions under which you use the car. Usually called "Normal" and "Severe" service.

The term "Normal Service" is defined as operating the vehicle under the following conditions:
"Where the vehicle is operated on clean, smooth dust and dirt free roads at a steady, constant speed and under moderate climate operation."

The term "Severe Service" is defined as operating the vehicle under any of the following conditions:
"Frequent short trips driving less than five miles, frequent driving in dusty conditions, extensive idling, trailer towing, sustained high speed operation, off road driving, desert operation, frequent starting and stopping, cold climate operation, short trip operation at freezing temperatures (engine not thoroughly warmed up, commercial service and stop and go driving."

If you operate under normal conditions, then you can follow the normal service schedule. But if you operate under severe conditions, the general rule of thumb is to cut the normal service interval in half. For example, under normal conditions you would do a lube, oil and filter change every 7,500 miles or six months, whichever comes first. Under severe conditions you would do it every 3,000 miles or three months, whichever comes first. Tire rotation is done every other service under normal conditions and at every service under severe conditions.

So, if you operate your vehicle under normal or severe operating conditions will determine when you need to do the service.