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My 2008 non-B9 Tribeca is great but I'm thinking about getting rid of it because I'm getting worse gas mileage than my husband's V8 Chevy truck! Any ideas what could be causing it? I have new, properly inflated tires. I just bought it about 6 months ago, so I unfortunately don't know too much else about the history. It's only got 107k on the odometer. Does this seem like a normal fuel economy? I am a little heavy footed, but not terrible. I also live in a small town where trips are usually never over 5 minutes.
 

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My 2012 gets 18-19 in suburban driving. These will never win any green awards but your mileage does seem very low. Hopefully the real mechanics on this forum will help.
 

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It's the short trips, the car never gets up to temperature. I assume you have already seen very low economy vs published rates on every car you've owned?

Make sure to follow 'sever' schedule for maintenance on all cars that you use due to these short runs!

Tom
 

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Discussion Starter · #4 ·
Thanks Tom, but I'm not sure what 'sever' is. I've only ever owned 2 other vehicles and both got just below the published rate for mpg.
 

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"Severe" (he forgot the 'e').

In the service manual, there are two recommendations for maintenance intervals, "normal" and "severe." If the majority of your driving is done in less than 5 minutes at a time, you need to follow the "severe" maintenance intervals.
 

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This car has many fluids and filters that should be regularly replaced....have they been ever serviced/replaced?
 

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If you have a model with navigation, you need to calibrate the system when you replace the tires... I'm not sure if that would make an 8-10 mpg difference, but before I calibrated mine (about a month after I bought the vehicle), the mpg was off by about 10% from what I was observing at the pump and on my odometer.

Menu (button) - Navigation Setup (on-screen) - Calibration (on-screen). Try this and see if it helps.
 

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Apparently there is a "hidden sequence" for non-navigation Subarus as well, although I don't know what it is.

ksn - that is extremely low mileage. I could see it happening to any Tribeca in good working order if you were only traveling a few miles before shutting the car off - staying in open fuel loop really hogs fuel because the car is trying to get the catalytic converters warmed up by running really rich.

If that isn't your average commute, I'd say there's something wrong. We typically get 16-19MPG in town and 22-26 on the highway in our '08. My wife commutes in it and that 16 figure is with her traveling about 6 or 7 miles to work in town, so it's barely gotten to temp at the end of her trip.
 

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tune up....maybe check the air filter and some new plugs? real fuel helps. no corn.

it wouldn't hurt to drive it for an hour once a week to heat everything up and cook off the moisture in the fluids.
 

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Lacking a check engine light (I assume it works and is not currently illuminated) the engine is running near design fuel efficiency. It's just running open loop all the time because it doesn't get warm which kills the fuel efficiency.

Tom
 

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are you calculating it by odometer at fill up or by the nav computer
 

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i agree but 15 on the highway should be in the closed loop arena...i would think something is off...stat stuck open, clogged cat, leaking copious amounts of fuel on the ground. it would be nice to see some fuel trim numbers or a knock count.
 

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Short trips. Colder weather (particularly if the vehicle idles for warm-up or if its use includes picking up kids in "the car line" at school/daycare).

And even the type of tire could all work together to bring a city-commuter's Tribeca down to that kind of gas mileage.

My '16 Outback - a 2.5i - only sees ~18 MPG via the onboard during the winter months, precisely because of these above factors.
 

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My dealership recommended that I use only mid-grade fuel. So I did for a while and one day decided to try standard fuel thinking the dealership was spewing crap. Sure enough my MPGs dropped from 19/21 to 12/13...I have used mid grade ever since.
 

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Short-trip driving fuel economy - synthetic oils

Short trips. Colder weather (particularly if the vehicle idles for warm-up or if its use includes picking up kids in "the car line" at school/daycare).

And even the type of tire could all work together to bring a city-commuter's Tribeca down to that kind of gas mileage.

My '16 Outback - a 2.5i - only sees ~18 MPG via the onboard during the winter months, precisely because of these above factors.
The gas grade (i.e. 87 vs 90 octane) can definitely play a role in a number of vehicle models on the market from multiple OEMS's. However, SHORT TRIPS (noted above as under 5 miles) is the biggest factor, for two reasons.

  1. The drivetrain lubricants (engine oil, trans oil, front diff, rear diff) are "cold" compared to "operating temperature".
  2. Subaru does not use synthetic lubricants. I'm speaking out of a strong technical base when I say that the manual's Severe and Standard maintenance intervals are exclusively based on petroleum oils... and Group I or II, not Group III. This speaks to either a lack of adequate lubrication expertise in Subaru's design engineering, or a lack of adequate "voice recognition" from their 1 - 3 experts.
When you use REAL (Group IV / V based, not Group II/III) synthetic lubricants, you get many automatic advantages including fuel economy improvements. But one of the big differences is fuel economy performance in the "cold" temperature range of short-trip driving.
I'm a newbie owner, 2010 'Beca bought Jan 2017. My engine oil change (full synthetic) bumped me a full 1.0+ mpg city. I'm looking forward to seeing where the trans and diff and power-steering fluids put me during the next several months. I'll find somewhere to keep people informed on it.
P.S. - great tip on the fuel octane. I'm going to evaluate that and see what the numbers tell me!
 

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My 2008 non-B9 Tribeca is great but I'm thinking about getting rid of it because I'm getting worse gas mileage than my husband's V8 Chevy truck! Any ideas what could be causing it? I have new, properly inflated tires. I just bought it about 6 months ago, so I unfortunately don't know too much else about the history. It's only got 107k on the odometer. Does this seem like a normal fuel economy? I am a little heavy footed, but not terrible. I also live in a small town where trips are usually never over 5 minutes.
I agree with the short trips theory. You are constantly running the car at low speeds. If you set the monitor to see what you are getting in real time. You will see 9, 8, 5.5 mpg/ This was the cause of my 12 mpg in the beginning when I reset it and then only drove a little bit around my neighborhood. Once I reset it and hit the highway, I have been 16 plus mpg. When was the last tune up?
 

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My dealership recommended that I use only mid-grade fuel. So I did for a while and one day decided to try standard fuel thinking the dealership was spewing crap. Sure enough my MPGs dropped from 19/21 to 12/13...I have used mid grade ever since.
I will try this as well. IM getting 16.9 avg right now using 87. I will use 89 or better and see wht I come up with in a month or two of driving. Of course I did a full vehicle fluid change recently.
 

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Great write up above. I will definitely try it out this spring.

I remember when I was a kid and hopes were high of this dream below. A Flux capacitor and a bag of trash to get from A to B.











 
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