So I had an O2 sensor go out about 6 months ago, I replaced it. The other ones appear to work but is it worth replacing them all to improve MPGs? Will this improve MPG?

Rig has 130k on it.

 

Yes you should do them all, as O2 sensors wear they do not react as fast and the voltage will not move as far up and down as a new one will. Buy a good quality O2 sensor like AC Delco or Bosch.

Will you notice a big difference? Probably not,but they do degrade over time sort of like spark plugs.

 

I'd argue that really the upstream ones are the only important ones. The downstream ones are solely to verify that the levels are lower after the cats. The upstream sensors do affect how the ECU controls the air fuel mixture. I just replaced both of my upstream ones as well.

 

That is true and a good point MixMan.

 

Did my downstream ones.... O-M-F-G!!!! Took a 1/2" breaker bar with a 24" pipe and I HAD to use my feet. This was after penatrating oil and heating and more oil and it still screwed up the threads and a HAD to tap them. Thinking of going header back with stainless and magnaflow...

 

Dang! I put some Kroil on the ones my my 2003 about 30 minutes before I tried removing them and they were not tough at all to remove.

 

Yea NEVER had ones sooo hard to remove, yea they stick and are a PITA but usually once you brake them free....
Lol the one side almost looked like it was pressed and rusted in ( I should post a pic ) its pretty hard to see that the old sensor even has/had threads... All in all it took me bout 9 hours to do two.

 

I love Kroil That is some great stuff,

 

Used PB and propane, I'll have to grab the old ones out of the garbage, you won't believe what the threads look like...