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Discussion Starter · #1 · (Edited)
Well we are fast approaching 60,000 miles on our 06 Tribeca. I noticed that our MPG's aren't what they use to be and mentioned it to my wife. She said the same thing they seem to have dropped somewhere between 2-4 MPG less than typical. I've seen this in the past and can usually attribute it to the front Oxygen sensor starting to go bad. Not bad enough to set off the light or make the car run poorly. Bad enough to effect the gas mileage though. I decided to order one and replace it. I know the sensor makers usually say they should be replaced at 60K but of course they sell them. I haven't been under the car yet but it seems to be a simple matter, I'll know for sure soon. I found a good price on a direct fit from drivewire:

http://www.drivewire.com/search/?Ntt=sensor&=&N=0&uts=true&t_event=true

I got the Denso W0133-1815466 direct fit for $126.95 not a bad price, what is bad is you will need two of them. If you look on the page you can see one below it for more money but I can't see what the difference would be. I'll try to do a scoobymods page and let everyone know how it goes and the results of the MPG's I'm hoping it improves somewhat.
 

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Discussion Starter · #5 ·
I don't think they need to be replaced, I just think it's a good idea. In all the Subaru's I've owned, after I replaced the front sensor the car got better MPG's. With one I started to have drivability issues. The car would hesitate at times and eventually the CEL came on. I checked my gas mileage and it went from 28 to 18. It ended up being the front sensor going bad. I replaced my sensor on my Forester XT at 80K miles and the mileage went up by about 3 MPG on average.

I'm slowly doing the 60K service and this is one of the things I wanted to get accomplished. I really don't think anyone needs to but I didn't want to wait till something went south is all. Plus I'm prolonging the pain of doing the spark plugs :)
 

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Peaty, thank you for the information! I always enjoy reading your threads. Very helpful! I just had the 60K done at the dealership which included the spark plugs but we have not seen any increase in MPG at all. I kinda thought we would see a little bit better mileage but no change. I may look into changing the O2 sensors as well. Please let us know if your MPG's went up! Thanks! Mike
 

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Thanks for the heads up on what to look for in future.

Peaty said:
I don't think they need to be replaced, I just think it's a good idea. In all the Subaru's I've owned, after I replaced the front sensor the car got better MPG's. With one I started to have drivability issues. The car would hesitate at times and eventually the CEL came on. I checked my gas mileage and it went from 28 to 18. It ended up being the front sensor going bad. I replaced my sensor on my Forester XT at 80K miles and the mileage went up by about 3 MPG on average.

I'm slowly doing the 60K service and this is one of the things I wanted to get accomplished. I really don't think anyone needs to but I didn't want to wait till something went south is all. Plus I'm prolonging the pain of doing the spark plugs :)
 

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Discussion Starter · #8 · (Edited)
Okay I want to give a quick update. The car is running fine after the sensor swap. The odd thing is according to the MPG display they have seemed to gone down a few MPG rather than up. Usually we see maybe 18 - 19 MPG but the last tank or two its been in the high 15's. There may be an explanation but it's too soon to tell. So far most all the miles on the car have been around town. Normally we see low MPG's when driving around town so the past two tanks may not be representative. I did just get new tires and the rolling resistance may have reduced the MPG's that has been known to happen. After the swap I did not do an ECU reset. I've unhooked the battery last night (cleaned it up and serviced it while I was at it - you can check the water level and such) and will hook it back up later and go through the normal deal to reset it properly. The Tribeca is at 58K miles and it's due for a plug change. I've ordered new spark plugs and will swap them out soon. The most likely culprit though is the fact that it's been very cold here lately. We all know that the cold weather makes the MPG's drop (takes longer for the car to warm up, more resistance in the oil flow longer) that coupled with the short trips is very bad for the gas mileage. Yesterday I changed the air filter too, it wasn't all that bad but I did it for good measure.

So it may be one or a combination of things we'll see. It's kind of too soon to tell but I'll report back as things progress. I will be traveling for half of next month so it may be a little bit but I will follow up :)
 

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Discussion Starter · #10 ·
I don't think so, supposedly the only "winter" gas we have is marked E10 on the pumps and that's the mid grade (89) and I've been putting in the premium the last few tanks. Unless my wife has put in the 89 but I don't think so. Normally my wife takes the car to work every day and I can get a good reading. Since I did the swap though she has gotten sick then my kid so she's been mostly home making very short trips. I think that in along with the super cold weather has much to do with it.
 

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Reviving an older thread here, but I have to ask: Peaty, did you ever figure out what caused the drop in your B9's MPG? Did things change once the weather warmed up?
 
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