03 X90 T6 Poor Gas Mileage (any suggestions)

trstjohn · Post by **trstjohn** » 27 Jan 2011, 17:43

I recently purchased a 2003 XC90 T6 2.9 (139k) and I believe I'm getting some pretty bad gas mileage..like 210 miles on a full tank. I recently ran some seafoam through the fuel tank, got an oil change with synthetic oil, but am still getting bad mileage.

Any suggestions?

I'm figuring it may be a good idea and cut my losses and get ride of the car.

Post by **JDS60R** » 27 Jan 2011, 18:12

Use stock air filter and change any oxygen sensor with more than 80K miles on it.

trstjohn · Post by **trstjohn** » 28 Jan 2011, 06:44

Wouldn't the car throw a CEL if the oxygen sensors was bad?

Post by **JDS60R** » 28 Jan 2011, 11:39

If it were broken= yes
If inaccurate or worn out =No
( the oxy sensors very slowly loose accuracy and the computer can not differentiate between differing engine conditions and a worn sensor)

By 80-100K they are far from accurate and generally cause the car to run rich leaving deposits in the chambers which raises compression, and can cause early detonation. Then the timing backs off and the car makes less power. Without regular replacement you get worse mpg, less power and more deposits.

Replacing oxy sensors is just a part of regular maintenance. Luckily you only need to do it about every 80-100K miles.

Read up on all of the threads and you will see that direct fit Bosch sensors (for most Volvos) is the best choice.
Save lots of money by using Matt's amazon link and buying them at Amazon. I install lots of them from Amazon and have yet to have a single issue on a Bosch direct fit.

Post by **boosted5cyl** » 28 Jan 2011, 14:40

John is this something that one can check for by monitoring the O2 voltages via OBD? I wouldnt mind checking to see if mine are getting "tired" but I dont have money to just throw at the car(s)...

Post by **JDS60R** » 28 Jan 2011, 16:38

Unfortunately checking for accuracy requires a gas analyzer. By 100K its gone -it needs one. Bosch spent a fair amount of time seeing how long they could really say "their" O2 sensor lasts. They still agree by 100K on a heated sensor - its gone.

The cycle rate can be graphed but the cycle rate usually slows down long after accuracy is lost. When cycling fails early you get lots of complaints of "no power/ low power"

I like to time the O2 replacement with a new set of plugs or other maintenance. Every 100K plus used car I buy gets a new one on it as part of its journey back to stage zero. I wouldn't put it on if I could get away without it. But folks love power and mileage.

PS -proper maintenance and use of a motor oil that has minimal burn off (exposes oxygen sensor to less contamination) play an important role in extending the life of sensors

trstjohn · Post by **trstjohn** » 29 Jan 2011, 12:31

Any specific Bosch O2 sensor suggestions?.

Post by **gshadow325** » 30 Jan 2011, 17:09

since my xc90 has 150,000k miles i think i am due for a SET of three. looking at the previous owners service records it did not mention anything about a CEL for oxygen sensors. I would assume they are still oem. Although he did see 22mpg oh the highway, i confirmed it with a trip to pittsburg from philadelphia. A good 500 mile round trip. Thats because my AOC/DEM did not work. Yes it does give you better gas mileage. Now since i have fixed the dem/awd i see 200 miles per tankfull. yes that bad.

So i bought the following bosch sensors
17188 Volvo Oxygen Sensor Front Right (S80 XC90) - Bosch 17188 (1) @ $148.95 = $148.95 - 10% coupon $134.06 FCPgroton
16541 Volvo Oxygen Sensor rear (S80 XC90) - Bosch 16541 (1) @ $86.34 Amazon
17135 Volvo Oxygen Sensor Front Left (S80 XC90) - Bosch 17135 (1) @ $101.30 Amazon

Eeuroparts was $510
fcpgroton was $438.40 - 10% $394.46

so fcpgroton and amazon shipped was $321.70 just got all order confirmations 3 minutes ago

I should be installing these sometime in the next two weeks. i will report back with my findings. FYI- car currently has NO CEL's, fresh plugs, pcv serviced @135k, t/b and w/p done @ 120k, lets see.....

trstjohn · Post by **trstjohn** » 02 Feb 2011, 10:16

Good news--
After replacing my air filter (K&N) yesterday, I was lucky enough to take a 75+ mile drive this morning. Just to test, I decided to fill upwith some mid grade gas as qwll. She's now reporting to get 295 on a full tank. Before the air filter change, car was saying about 220.

Post by **gshadow325** » 28 Feb 2011, 05:01

i dont know if the filter panel will net you that much gain. I do know for a fact that changing out the O2 sensors will net me a 20% increase in fuel economy. read my post here https://www.matthewsvolvosite.com/forums ... 58#p173658