Change O2 sensors?
Thread Starter
Race Director
Joined: Dec 2002
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From: Baltimore suburbs Maryland
Change O2 sensors?
Anyone change their oxygen sensors on a higher mileage car? Im not getting any codes but at 135k miles I'm sure mine are getting a little tired. Anyone change them out? Hopefully get a little better MPG... 
Tech Contributor
Joined: Jan 2007
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From: Dyer, IN
Why fix what's not broken? What type of mileage do you get now?
Thread Starter
Race Director
Joined: Dec 2002
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From: Baltimore suburbs Maryland
I get lower mid 20's in mixed driving like 23-24 MPG. If it's mostly stuck in city traffic driving, it drops to like 18 or 19. I know some members reported getting even higher mileage. I keep the car tuned up, new copper plugs every 15K, wash the air filter, etc.
The cost of O2 sensors would quickly offset any "savings" from added MPG for a while.
The cost of O2 sensors would quickly offset any "savings" from added MPG for a while.
Tech Contributor
Joined: Jan 2007
Posts: 19,462
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From: Dyer, IN
I get lower mid 20's in mixed driving like 23-24 MPG. If it's mostly stuck in city traffic driving, it drops to like 18 or 19. I know some members reported getting even higher mileage. I keep the car tuned up, new copper plugs every 15K, wash the air filter, etc.
The cost of O2 sensors would quickly offset any "savings" from added MPG for a while.
The cost of O2 sensors would quickly offset any "savings" from added MPG for a while.
My thinking, if they're not throwing any codes, then they're still in range. You can have them monitored though if you're curious to how the O2's are responding. There are many ways to optimize gas mileage such as: proper tire pressure, driving habits, maintenance, etc. In reality, if gas mileage is a big concern for you, then a V8 anything is not going to serve you well right now.
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From: Granby, MA
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Do you have an oil consumption problem that requires you to change plugs every 15K? I think the last time I changed plugs at that frequency for a daily driver, was the last time I worked on a carburetor
My thinking, if they're not throwing any codes, then they're still in range. You can have them monitored though if you're curious to how the O2's are responding. There are many ways to optimize gas mileage such as: proper tire pressure, driving habits, maintenance, etc. In reality, if gas mileage is a big concern for you, then a V8 anything is not going to serve you well right now.
My thinking, if they're not throwing any codes, then they're still in range. You can have them monitored though if you're curious to how the O2's are responding. There are many ways to optimize gas mileage such as: proper tire pressure, driving habits, maintenance, etc. In reality, if gas mileage is a big concern for you, then a V8 anything is not going to serve you well right now.
For you, as mentioned I agree with lucky. When it comes to 02's, don't change them till the check engine light comes on and tells you your now outside your range. The 02's get lazy over time and will trigger the codes and check engine light....but honestly when I changed mine out, I noticed no difference in performance or MPG. My car has always gotten around 25mpg average (combined city and highway). At $60 each for the fronts and $70 each for the rears....this is pretty costly to do just for maintenanace. $260 for sensors! That would make me think, there better be a problem.
Last edited by XtremeVette; Aug 7, 2008 at 12:12 PM.
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From: Jacksonville Florida
If you are at 135k, I would definitely change the 02 sensors.
The OBD2 system will not detect if the 02's have drifted slightly out of range. Slightly out of range can cause a dramatic loss in gas mileage.
02's like any other precision measuring device should be replaced at regular intervals. The most I recommend putting on a set is 80k, and then they get changed.
The OBD2 system will not detect if the 02's have drifted slightly out of range. Slightly out of range can cause a dramatic loss in gas mileage.
02's like any other precision measuring device should be replaced at regular intervals. The most I recommend putting on a set is 80k, and then they get changed.
Tech Contributor
Joined: Jan 2007
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From: Dyer, IN
If you are at 135k, I would definitely change the 02 sensors.
The OBD2 system will not detect if the 02's have drifted slightly out of range. Slightly out of range can cause a dramatic loss in gas mileage.
02's like any other precision measuring device should be replaced at regular intervals. The most I recommend putting on a set is 80k, and then they get changed.
The OBD2 system will not detect if the 02's have drifted slightly out of range. Slightly out of range can cause a dramatic loss in gas mileage.
02's like any other precision measuring device should be replaced at regular intervals. The most I recommend putting on a set is 80k, and then they get changed.
I suppose you could chalk it up to an oil company conspiracy, but the automotive sensor guys wouldn't allow that....or would they?
Last edited by lucky131969; Aug 7, 2008 at 03:30 PM.
Thread Starter
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From: Baltimore suburbs Maryland
Do you have an oil consumption problem that requires you to change plugs every 15K? I think the last time I changed plugs at that frequency for a daily driver, was the last time I worked on a carburetor
My thinking, if they're not throwing any codes, then they're still in range. You can have them monitored though if you're curious to how the O2's are responding. There are many ways to optimize gas mileage such as: proper tire pressure, driving habits, maintenance, etc. In reality, if gas mileage is a big concern for you, then a V8 anything is not going to serve you well right now.
My thinking, if they're not throwing any codes, then they're still in range. You can have them monitored though if you're curious to how the O2's are responding. There are many ways to optimize gas mileage such as: proper tire pressure, driving habits, maintenance, etc. In reality, if gas mileage is a big concern for you, then a V8 anything is not going to serve you well right now.
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Original Founding Member!
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From: Granby, MA
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If you are at 135k, I would definitely change the 02 sensors.
The OBD2 system will not detect if the 02's have drifted slightly out of range. Slightly out of range can cause a dramatic loss in gas mileage.
02's like any other precision measuring device should be replaced at regular intervals. The most I recommend putting on a set is 80k, and then they get changed.
The OBD2 system will not detect if the 02's have drifted slightly out of range. Slightly out of range can cause a dramatic loss in gas mileage.
02's like any other precision measuring device should be replaced at regular intervals. The most I recommend putting on a set is 80k, and then they get changed.
Very confused by this.
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From: Granby, MA
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Point taken; however, the OP is not suffering a "dramatic" loss in gas mileage. Also, if this is true about OBDII, then thousands of cars on the road could have O2's slightly out of range, and be suffering poor gas mileage. If this is true, then it makes one wonder why it would not be a scheduled service item on all cars, or at the very least, a scan to verify integrity.
I suppose you could chalk it up to an oil company conspiracy, but the automotive sensor guys wouldn't allow that....or would they?
I suppose you could chalk it up to an oil company conspiracy, but the automotive sensor guys wouldn't allow that....or would they?
Tech Contributor
Joined: Jan 2007
Posts: 19,462
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From: Dyer, IN
Jeff this is out of the 2002 service manual that I have, does yours read differently?
* 166 000 km (100,000 mi) Replace the spark plugs. This is an emission control service. Refer to footnote [Dagger].
* Inspect the spark plug wires. This is an emission control service. Refer to footnote [Dagger].
* Change the automatic transmission fluid and filter if the vehicle is mainly driven under one or more of these conditions:
o In heavy traffic where the outside temperature regularly reaches 32°C (90°F) or higher.
o In hilly or mountainous terrain.
o Uses such as high performance operation.
If the vehicle has not been used under any of the severe conditions listed previously and, therefore, has not had the automatic transmission fluid and filter changed, change both the fluid and filter.
Manual transmission fluid does not require change
* 166 000 km (100,000 mi) Replace the spark plugs. This is an emission control service. Refer to footnote [Dagger].
* Inspect the spark plug wires. This is an emission control service. Refer to footnote [Dagger].
* Change the automatic transmission fluid and filter if the vehicle is mainly driven under one or more of these conditions:
o In heavy traffic where the outside temperature regularly reaches 32°C (90°F) or higher.
o In hilly or mountainous terrain.
o Uses such as high performance operation.
If the vehicle has not been used under any of the severe conditions listed previously and, therefore, has not had the automatic transmission fluid and filter changed, change both the fluid and filter.
Manual transmission fluid does not require change
Original Founding Member!
Joined: Jul 1999
Posts: 9,037
Likes: 88
From: Granby, MA
Cruise-In 1, 3, 9. 10 & 11 Veteran
Jeff this is out of the 2002 service manual that I have, does yours read differently?
* 166 000 km (100,000 mi) Replace the spark plugs. This is an emission control service. Refer to footnote [Dagger].
* Inspect the spark plug wires. This is an emission control service. Refer to footnote [Dagger].
* Change the automatic transmission fluid and filter if the vehicle is mainly driven under one or more of these conditions:
o In heavy traffic where the outside temperature regularly reaches 32°C (90°F) or higher.
o In hilly or mountainous terrain.
o Uses such as high performance operation.
If the vehicle has not been used under any of the severe conditions listed previously and, therefore, has not had the automatic transmission fluid and filter changed, change both the fluid and filter.
Manual transmission fluid does not require change
* 166 000 km (100,000 mi) Replace the spark plugs. This is an emission control service. Refer to footnote [Dagger].
* Inspect the spark plug wires. This is an emission control service. Refer to footnote [Dagger].
* Change the automatic transmission fluid and filter if the vehicle is mainly driven under one or more of these conditions:
o In heavy traffic where the outside temperature regularly reaches 32°C (90°F) or higher.
o In hilly or mountainous terrain.
o Uses such as high performance operation.
If the vehicle has not been used under any of the severe conditions listed previously and, therefore, has not had the automatic transmission fluid and filter changed, change both the fluid and filter.
Manual transmission fluid does not require change
Tech Contributor
Joined: Jan 2007
Posts: 19,462
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From: Dyer, IN
Yep, saw that too. Its not in that maintenance section at all lol (Good thinking GM). I found it by accident skimming over pages when you had me look to find the thing about the fuel filter lol....now if I can just remember where the hell I saw it! Oh by the way...I sent an email to Gene Culley about the fuel filter. He said basically to use the manual as a reference only.. GM cut a lot of information out to save time and money. He said any item that we feel should be a maintenance item probably is and to use our better judgment as far as when to change them.
