My car is almost at 115k miles. My gas milage is not great. I get anywhere from 17 miles to 21 miles per gallon (mostly around 19) with a combination of freeway and city driving. If I do mostly freeway driving I can get up to 23 miles or so. I see many posts here where people get way more than this. I replaced my knock sensor a while back(only code I had), as well as my fuel filter. After doing this my miles per gallon went up, it would sometimes go as low as 13 or 14 miles per gallon. I have no codes, my cel has never turned on. I only found out about the knock sensor after I checked for stored codes, I thought my hesitation was just due to my car getting older, but it was the KS. My question is this, is there a certain time that you should replace the O2 sensors as in preventive maintenance, or just when they trigger the check engine light?

 

Some will say you should replace the O2 sensors because they get "tired" while others say if it doesn't bring up a CEL, then don't replace it.

At 90k miles now and no CEL, I replaced the O2 sensors (front only) and maybe it is all in my head but the car just feels like it revs up a little better and I get better throttle response in day to day driving. Heck, I did the MAF ground mod at the same time so who really knows.

With as many miles as you have, if you have a few bucks lying around, I say replace them. Get the Bosch sensors WITH harness.

 

Thanks for the reply.

 

I have 120k and the CEL just came on for both right and left front o2 sensors. how hard is it to replace these? can i buy them at auto parts stores, or is it better to buy from a nissan dealer like courtesy or jerry rome?

 

dont buy them from the dealer, there liek $200+ each and i think theres 3, buy htem from drivewire.com