Mercedes-Benz Forum banner
1 - 10 of 10 Posts

·
Registered
Mercedez Benz E320
Joined
·
161 Posts
Discussion Starter · #1 ·
I have 114K on my 2001 E320. I have performed most 100K recommended maintenance with the exception of the oxygen sensors. My gas mileage is still ok based on on traffic conditions and my driving habits. Should I install new 0xygen sensors as a proactive measure or wait for it to throw codes? Also, I am still on original cats. I wonder if changing the sensors would help cats last longer. Also, perhaps gas savings may justify the investment? It costs approx $575 for all for sensors. Any advice appreciated.
 

·
Premium Member
2004 CLK 240 Coupe
Joined
·
11,385 Posts
My gas mileage is still ok based on on traffic conditions and my driving habits. Should I install new 0xygen sensors as a proactive measure or wait for it to throw codes?
No. There are some tasks that preventive maintenance is applicable to. I don't consider changing the O2 sensors is one of them.

Also, I am still on original cats. I wonder if changing the sensors would help cats last longer.
Again no. If you consider what the function of the O2 sensors is, you will agree that nothing there affects the lifetime of the cats, provided the engine perfornance is normal. I would wait for them to fail.

From the WIS...The O2 sensors record the residual oxygen in the exhaust gas and send a signal to the engine control unit . (for mixture management)

O2 sensors upstream of the cat. The O2 sensors are for:

* lamba control
* self-adaption of the mixture formation
* function chain tests

O2 sensors downstream of the cat. The O2 sensors are for:

* 2 sensor control
* monitoring cat efficiency
 

·
Registered
1959 220S cabriolet, 1983 240D original owner, 1999 E300 turbo diesel, 1988 560SL, 2003 SLK320
Joined
·
3,513 Posts
There was another thread on here a week or two ago with the same question. My reply was to wait for the code to be thrown. However, at least two members indicated that the sensors do degrade over time and even though they are still within specs, they tend to decrease mpg and engine performance. One of them said that such a note may be shown in WIS, i.e. to change them at 100,000 miles. None of the service literature I have show that, but I'd like to know if it is listed somewhere.
 

·
Registered
Black on Black 1997 E420
Joined
·
267 Posts
To answer your questions: Yes, no & yes.
It wouldn't hurt to change out the sensors, especially at 100k miles.
Purchase your sensors from Autohausaz.com for about $200 less and you'll be happy.
 

·
Registered
99 E430, 01 E430 Sport, 00 SL500
Joined
·
3,261 Posts
I wait for codes because
1. The codes are there for a good reason, "replace me!".
2. The car computer is programmed to optimize performance when sensors are within specs.
3. It costs much more than $10 to replace a working sensor.
4. New sensors come with 3-month, 6-month warranty. The ones with 12-month warranty are the most expensive.
5. No proof for lower mileage or performance when sensors are still within specs.

By the way, in another post about O2 sensors, some experts here warned me about washing O2 sensors with gasoline. I tried soaking over night, washing to save some bucks, it didn't do anything good. The bad sensor remained bad with the same check engine code
 

Attachments

·
Registered
'01-E320 & 02-ST2
Joined
·
31,631 Posts
The check or replace at 100K spec comes from Bosch; I'm not aware it appears anywhere in MB literature. It may just be a moneymaking scheme for them; who knows?

The planar sensors in the M112/113 seem to be more stable than the thimble-style, so if your mileage is okay I'd probably leave well-enough alone. I did mine early since I was DIY-ing the cats anyway; once you've dropped $1,100 what's another $240 (universal Bosch), right? :D

That said, I would be proactive about codes. Don't wait for a CEL, rather check codes every month or so to see if there are any pending.
 

·
Registered
99 E430, 01 E430 Sport, 00 SL500
Joined
·
3,261 Posts
On my 99 E430, the left rear O2 sensor failed at 80K miles; the car now got 129K miles with 3 original, 1 new sensors. Gas mileage has been consistent. So replacing the sensors at 100K miles would have been a waste of money.
On the 01 E430 at 76K miles, the two front O2 sensors were flagged as bad with CEL, I replaced them a few days ago. I used some coupon at advanceautoparts to get posi lock Bosch for about $110 for two. It took more time to cut to install but I saved $100 over the direct fit.
All of replaced sensors had caused CEL to come on.
I used to have a Carchip that plugged into the car's OBD port. It could log the sensors' voltages to show the range, I misplaced it somewhere in the garage.
 

·
Registered
1922 Ford T no OBD, no ECU, no SCN
Joined
·
37,842 Posts
Unless you can actually measure the sensors performance like mbvis did, I think replacing makes lot of sense.
I bought my first W210 with gasoline engine about 6 years ago when it had 70k on it. The car had pretty s***y gas mileage, what I was blaming on CA diluted gasoline, wagon and 4-Matic, but after making 25,000 miles on it the CEL come on and I changed MAF and spark plugs at the same time. To my surprise the car's mpg improved by 15%.
So at 20 mpg, 25,000 miles the 15% higher fuel consumption equals to about $560 worth of fuel that was burned because of MAF going out of spec, but not triggering CEL yet. I don't drive gasoline vehicle anymore, so don't have the problem, but my conclusion is, that if you have doubt -buy new sensor, swap it and see if you notice difference in mpg. The worse thing might happen is that you end up with spare sensor that will be needed sooner or later anyway. Or get the advanced scanner that will tell you the details.
 

·
Registered
2001 SLK 320(222K Miles), 2002 E320 Special Edition(186K Miles)
Joined
·
3,472 Posts
I replaced mine at 110K with no CEL. No difference in fuel consumption.
 

·
Registered
2013 E350/41k, 1997 E320/290k, 1999 FJ100/256k
Joined
·
314 Posts
Replaced front O2 in our new to us car, had hunting idle when cold, no codes pending or thrown. Car ran smoother - hunting idle amplitude is less, and seems peppier when cold.
However I also switched from Costco to Shell/Chevron and the same time. Gas mileage is slightly better..

So seems to make some difference - and I feel better also knowing got a fresh part in there. Mileage is still 17-19 around town so might consider MAF next..
 
1 - 10 of 10 Posts
Top