1 pointI only put on 5000 miles a year, so I change it every 15,000 miles. When the car is out of its extended Ford warrantee, I'll probably do it every 10,000 miles. At this point, if it blows, I'm still under warranty so every 15,000 miles is what I decided to do. I have the dealer do it. If I recall correctly, it's about 100 bucks or so. I did have to convince them over time to do it........ as they gave me the standard "FORD says it's lifetime fluid".