After replacing the o2 sensor I have gone from 12mpg city/ 15 highway to 19mpg city/ 29 highway. The old O2 didn't look so bad but it smelled like oil. I think before I replaced my PCV the oil burning may have damaged it, huh?

wow, how old was the old one?

It was original.

WOW , after 115k, i'd say so.

I'm at 137K on the original sensor and still getting 25 mixed city/highway

I'm at 218k w/ original

Oh ya, to stay on topic........Congratulations on the mileage bump.

You may want to consider it.

As with any electronic or mechanical piece, some wear better than others. No one can really say what is working good/bad w/o putting an O2 onto a scan tool and watching it flip flop. Even then..what'* really good and whats bad?

I guess you'd need to record the data and over analyse it to a point that putting in a new one if you felt the need would be best.

If it'* not broke, it doesnt need to be fixed. Travis is getting over 30mpg consistently. Who knows, replacing it might make his mileage go down a little. Factory Freak.

I,m just going by my own experience, i just changed mine yesterday(143k, and i noticed on my scan tool(cp9145) it was showing inconsistencies(staying on rich longer than lean instead of cycleing evenly between the two), a sighn of a bad O2 senser. so if mine at 143k is bad i'd bet one at 200k is't much better.