Most miles you had on a catalytic converter?

[SHOZ]

I get the P0420 code on my Accent at 157k miles. I can clear it and it will come back in a week or so. I have tried the 'Italian Tuneup' and it does seem to help. I usually go 5mph to redline in 3rd gear, around 100mph, shifting at the redline in the lower gears.

I was considering taking the primary O2 out and pouring a couple bottles of Seafoam through it when cold. The cat sits vertical in the front so that would be fairly easy t do with the O2 out.

My sons 4 cylinder Chevy Malibu had the cat clog up but that was from a bad coil and misfiring and at about 150k. The replacement aftermarket cat still sets the P04320 code though..

 

[JTK]

For the OBDII compliant vehicles in my family, it seems the high 100K mile range and ~10yr point is when catalyst inefficiency codes start popping up. These were all used purchases, so no real way of knowing prior care.

For one owner OBDII vehicles, it seems the ~200K mi point is a fair average before a catalyst related code is set.

All catalyst in this realm has a finite lifespan because of the way it's used.