O2 Sensor Life Expectancy?

I have a 2002 Z-71 with 165K miles.  I've owned it 2 1/2 years (since 136K miles).  Previous owner told me the things he replaced and O2 sensors wasn't on the list.  It runs fine but I'm a tinkerer and am wondering if replacing them as a matter of course is a good idea.  No code or anything.  It has started using more fuel lately and I'm attributing that to cold weather and winter fuel but can't help but wonder.
Thoughts?
Thanks!

I would love to get 16.1 average. But I do mostly in town driving and have 4.10 gears. Thank God gas is so much cheaper. When O2 sensors first came out on cars, yes I am old enough to have worked on those vehicles, the recommendation for replacement was 60k if I remember correctly. If you got extra cash and like to get dirty I would replace with all those miles on there because they are there to monitor and protect the catalytic convertors. For a few days before you actually try to remove spray penetrating fluid on the threads and let them soak. I have seen stubborn sensors come out taking the threads with them.

Yeah RR that 16.1 is since purchase.  Lately it's been sub 14 and most of my driving is highway.  I thought I'd heard they needed replaced on sort-of a schedule but wasn't sure.  I might price them.  Good call on the penetrating oil.

They could be a source of the mpg loss. I think the "recommended" replacement interval went to 100k for the heated sensor. I looked in my 02 AV manual and saw no recommendation at the 100k interval schedule but found on line several recommendations for the mileage.

Avalanche Manual = No change un less required.

Peeps with money to burn = Change every 100K miles

Me... I will wait for the light to tell me they are not working or see a sudden drop in mpg...

LOL! My dad told me one time that is breakdown maintenance instead of preventative maintenance. At times when I first started out pumping gas and checking oil I would carry the oil dip stick to the lady driver and show her there was no oil level reading on the stick and recommended adding oil and she would say, "I don't have a light on at the dash so it is ok and don't add oil." Oh well!

Not like the 02 sensor is a moving part or if it fails you will be stranded or what not.

Nothing happens if rear one fails other then you do not know when cats fail.

front one fails and you drive too long with idot light on you can ruin and clog cats..

do you change all the engine sensors no...
we change them when they fail....

anything more is wasting $$$

Changing O2 sensors is like changing spark plugs.. You SHOULD do it to maintain your drivability. I have also seen suggested that you should consider getting your injectors rebuilt after 100,000 miles as well. They don't need new units but rebuilding the old ones will save gas mileage as well. Injector cleaner does nothing for warn injectors.

So Plugs, Wires, O2 sensors and injectors should be done every 100,000 miles.. Spark plugs should be done about every 50,000 miles if you can.. They start showing measurable wear after 50,000 miles but should last 100,000 before major failures.

Rodney

I don't know about that, I have had several cars and trucks for many years and never replaced a 02 sensor. The only one I had a issue with was my 1988 S10 with 188,000 miles I donated it to the VOA because I did not want to deal with it.

But really all you have to do is keep it in tune and add some Fuel system cleaner twice a year and you will not have a problem.

A car is good for 110,000, a truck should last much longer without emission problems.

So change plugs and wires at 75,000
Change/clean(CAI) the air filter twice a year, if you have a stock intake change the filter each season 4 times a year.

I did notice a wave pattern on my left bank 02 sensor but the system cleaner fixed that.


I know some folks use snake oil (AKA) Sea Foam really bad idea.

Thanks for all the replies and comments guys. 
I get the unnecessary maintenance and I definitely don't have money to burn but we're talking about 165K and a sudden drop in gas mileage here.  I'm leaning toward doing it (I have an "in" to discount parts) but I'll probably drive it a few more weeks and watch the fuel economy.  I changed the plugs, wires, belts, fan clutch; knock sensors (there was a code on them) right after purchase and have been rewarded with good performance and economy since.  The PO had put new injectors in just after 100K.  I just put new tires on and had the front end reworked and aligned so have to recover from that financial hit too.
Thanks again and keep the comments coming.

Good luck.

Over the years I have seen studies that mention sensor life and my prior posting was based on the idea that the studies I saw mentioned you SHOULD change them because they saw measurable differences at those mileages. Does it cause a failure or premature wear of cats or such? Probably not.. But I figure for the cost of the sensors it is not a big deal. I would rather the comfort knowing it is running most efficient than wait for a code and I am un prepared to fix a failure. Which is why I replaced the rear end, transfercase and transmission over past year. And from the looks of the internals it was good I did. They might have went 20k-30k before failure or maybe even 100k before failure but I would rather have paid the few dollars now while I plan for it than wait until I had a failure down the road on a long trip or something. So I paid $3000 for all three to be rebuilt instead of paying twice that if I wait for them to fail and have to replace many more parts.

Just saying preventative can make a big difference.

Rodney

Naw real world, drive it.

I have been driving since 1970.

changing a SENSOR before or it breaks or after it breaks (O2, MAF etc) costs the same.
Spark plugs & wires & Fuel injectors are NOT sensors and a separate discussion

Not sure how it cost more or less after it fails...
the labor and part cost to change a MAF or O2 SENSOR is the same whether it needs it or not.

I have yet to read the logic or study or anything that says replacing on a TIME basis is the thing to do.

but this is a Free country and you can change them whenever ya want... I am just trying to spread a differing opinion where if left alone these engines etc will last a long time by just follwing what Chevy says in the manual..

My 2002 is still running like the day I got it back in Sept 2001 after 140K miles.
NO issues except for needing a little Dielectric grease on the TB connector years ago.

I will make just one more rebuttal and then drop this..

Rebuilding the Injector will help with the atomization and proper modulation of fuel into your cylinder. Will also take care of any carbon build up and prevent failure due to being worn out. I have seen studies that state it is a good idea to do. If you do a cost advantage study and rebuilding your injectors makes a half mile per gallon difference at 100,000 miles and maybe a whole gpm at 200,000 miles is it cost effective to change it out? Or just wait until you have hard starts... Is it necessary to do? No, you can wait until your injectors start failing and maybe hope that injector cleaner does something... Have I changed out the injectors in my truck? At 240,000 miles? No.. I will likely do so in the next year however.. It just wasn't a high priority with the other stuff I am doing.

O2 sensors... Do they have to be replaced? No.. You can wait for them to fully fail (And for the secondary O2 sensors I wouldn't change them unless they do fully fail.) They have been shown to become more erratic after a certain point and your fuel efficiency will suffer. We could be talking as little as a half mile per gallon or 2-3 or more miles to the gallon. This again is a cost evaluation.. You CAN run with bad O2 sensors although it can drastically reduce your cats lifespan. The secondary O2 sensors do nothing but warn of a possible cat issue and can be disabled with no ill effects. Front sensors can directly effect your fuel mileage as much as any other sensor.

Plugs, Wires... These wear out at a much faster rate and have a plan failure rate. You should replace at the worst every 100,000 miles. These are very cheap and to maintain best efficiency you should change platnum plugs sometime between 50,000 and 100,000 miles. Every additional mile you get out of them is that much less you need to have the next set in for but as I have previously mentioned I have seen  a couple different studies that stated at 50,000 miles your plugs show a measurable wear. 100,000 miles is if your lucky...

The time to change is like an oil change or anything else.. It is an estimated guess based on the mean failure rate of the component. You could easily get 200,000 miles out of a set of plugs and never have an issue. You might get 100,000 miles out of an air filter too. But an air filter you can actually inspect. A plug you can inspect as well. Things like O2 sensors or injectors you really can't inspect unless you do it under lab conditions and have a special tester to test them against others.

The main point of Preventative maintenance is to replace components you know will wear out or go bad before they do. The art to them is to know based on their age and possibly condition when the best time to do that without wasting life of that component. Corrective maintenance is fixing something that is already broken. Personally I tend to like to change stuff out that is showing signs of wearing out before it actually breaks causing other issues or other things to break. But you can do as some do and never fix anything and just sell your vehicle when the list of repairs is long and you don't want to deal with them knowing you will have to spend a lot of time and money all at once or junk it. It is totally ones own choice.

I only mentioned the things I did because if you want your truck to run optimally you really should take a good look at these items as replace items. No different than changing out the Knock sensors and harness when someone had an intake leak... You KNOW its going to be an issue so take care of it before it is...

Rodney

Great post Rodney.  I'm firmly in the preventive maintenance camp.  I'd rather change a part "prematurely" in the comfort and safety of my garage (or pay a pro to do it) than run it to failure because I didn't have a light and risk collateral damage or being stranded.  IMO anyone who does their maintenance based on a light and nothing else is less than wise.  My Dad didn't do any maintenance (other than oil changes) unless the vehicle wouldn't start or drive right.  I watched him wage war with a number of cars over the years and he generally ended up on the losing end.  Maybe I've gone too far the other direction.
Also this link is a good read re. O2 sensors in general.  It only stands to reason that something that's forced to live in that environment could deteriorate as a result.  I'll probably be changing them and I'll report back if there's any difference afterward.
Thanks all!

http://www.autotap.com/techlibrary/understanding_oxygen_sensors.asp

I routinely replace my 02 Sensors at 100,000 miles error code or not, always see a 2-3 mpg jump in gas mileage and an improvement in engine smoothness so IMO it's well worth it.

SO when do I change the MAF sensor?

Ps I am getting the same mpg I have since I bought the truck...
16-17 mpg...

I've never had a injector go bad either, just kept the system clean

redheadedrod said:

...
The main point of Preventative maintenance is to replace components you know will wear out or go bad before they do. The art to them is to know based on their age and possibly condition when the best time to do that without wasting life of that component. Corrective maintenance is fixing something that is already broken. Personally I tend to like to change stuff out that is showing signs of wearing out before it actually breaks causing other issues or other things to break. But you can do as some do and never fix anything and just sell your vehicle when the list of repairs is long and you don't want to deal with them knowing you will have to spend a lot of time and money all at once or junk it. It is totally ones own choice.
...

Click to expand...

You missed one of my points ..
how much does it cost to replace an o2 Sensor when it is BAD versus replacing @ 100K miles?
the same... so why not wait until it fails?
What is the savings of replacing early?

Now if were to drive another 1000 miles or so with a bad o2 sensor (or check engine light) then yes they are more than likley going to have to fix other things....

PS this is good debate for all....
Like the dino versus synthetic oil debate...

I buy my 02 sensors from Rock Auto for about 40 bucks each. By way I only replace the primary sensors. I soak the threads with penetrating oil, use an 02 socket and it typically takes less than 15 minutes. As for dino vs synthetic I have 249,100 miles on my 2002 Z-66, used Valvoline high mileage 10W30 dino/syn blend for every oil change, never changed oil till the change oil light came on. Engine still runs great and uses no oil. As a matter of fact I towed a 26 foot camper for 6800 miles at 226,000 and only used a pint of oil.

BTW MAF sensor is original I just clean it once a year.

junkyarddog said:

.... 10W30 dino/syn blend ...

Click to expand...

Finally an oil for those dyno/Synthetic Fence sitters... I forgot about the mix/blend types.

So do you think of it as synthetic or dyno if you had to choose.

There's a difference between waiting for an O2 sensor to go bad versus other sensors in that unlike most other sensors the performance of the O2 sensor can degrade over time whereas the others are pretty much either working or not.  MAF being an exception to that but that is due to it being dirty which can be remedied without replacement.  O2 sensors also can go belly up in an instant but if they don't they start to degrade just as plugs and wires do.  Waiting for a light to come before changing the O2 sensor is like waiting for misfire codes before deciding to change plugs and wires.  They degrade, everybody knows it.  They react slower to changing air/fuel ratio.  The way our PCM's work that means the short term fuel trims are swinging back and forth farther than they should be.  That means your AFR on average is a bit more "off" than it needs to be which can cause mileage and emissions to suffer.  If you want your engine and fuel economy to be all that it can be they should be changed around 100k miles.  It's one of the things I plan to do next time I change the vette's oil.

Well I replaced the two upstream O2 sensors (not a bad job at all) and my first tank showed a dramatic improvement in economy.  (See my Fuelly link)
To be fair, the weather was warmer than normal and it was a mostly highway tank but lately even on the highway tanks it hasn't been nearly this good.
I even replaced the ones on my 2003 GMC Yukon and while I haven't done a proper calculation the DIC shows over 19 mpg over the last 100 miles-mostly highway.  This is up at least 2.5 mpg and probably closer to 3. 
The jury is still out but early indications are favorable and compelling.