Red_LX
Unless your engine is running overly rich, or you've put some weird additives through the fuel system, a cat should last at least 100,000 miles. Why does yours need replaced, is it clogged?

Pedro S
government regs make manufacturer responsible foe 10 yrs...

Blue
They usually last for at least ten years, even with silly little journeys that damage them the most. My old company car was a 1998 focus one of the first ones, that went to 120k with the same cat, and never really needed any real repair work. Good maintenance helps though.

handsonhips101
depends, should last a fair few miles, depends on how the cars used, thrashing it will cause quicker breakdown as will knocking the cat on bumps, kerbs etc. once the cars out of warrenty anything can happen, a secondhand jobbie will be far cheaper than a brand new one, some scrappys in the yellow pages delver and give a warrenty on used parts, i paid £35 for a cat for my 1600 zetec fez, £130 from ford!

mooniecamper
no set time as to how long they last your car will tell you when its shot. to cut a very long story short there is 2 sensors in the exhaust one before and one after the cat when these figures go out of range in the managment system it will put on your engine fault (mil) lamp on