I did a quick search, saw different results. My truck has 108,000 hard miles.
The cats were replaced at 65,000 miles by the dealer. However the oxygen sensors are original .

My truck is a 1999 Silverado Z-71 5.3, Auto with basic mods. Cold AIr intake, exhaust, 02 computer, 02 injectors, and Finish Line Level 5 tranny.
Tuning by allen nelson, but before he started, it ran a year or so with hypertech.

My mileage has dropped, plugs look great.

What oxygen sensor is everyone using, and do I need to replace all of them ?

Thanks,

Brian

 

Go OEM for O2 sensors. I got a Bosch pair and they fit and everything, but I got a check engine light and my MPG dropped (And I reset the light a few times but it still came back), got an OEM pair to replace them, MPG increased 2-3 and check engine light went off.

I replaced them at 80k when gas prices were hovering around $4 and picked up 2-3 mpg. I only replaced the front 2. I don't think you gain anything by replacing the rear ones, but someone else please address this too.

 

ACDelco is the best sensor. Don't bother with the rear sensors.

 

Just curious, what led to the Cat change?

 

do you know if you can get the delco sensors from local parts store or dealer only? Also do you have a part number by any chance?

 

GM parts direct. don't know the part number, do a search on the huge thread about gm part numbers, I'm sure it's in there.

 

The code thrown suggested cat failure. Dealer replaced em no questions asked..

 

OEM for sure