my wifes car is a 95 mystique with about 110K miles on it. i thought that the timing belt went on it last weekend. it turns out that the belt was actually still good but the tensioner pulley broke. the belt was actually still good but put a new one on anyhow. i do not believe the zetec is an interference engine. Put a new belt and tensioner on and the car runs fine.
if you can handle the hassle of getting it towed when it breaks then i say let it go until it does. otherwise change it at about 100K miles. while you are there changing the belt, change the tensioner too. i am not the only one on this forum that has reported the tensioner breaking!
