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2002 Subaru Outback's miserable gas mileage

Older (2002) Subaru Outback LLBean Edition 3.0L HD engine allegedly with 114000 miles; getting miserable gas milage-15 mpg. What problems may be causing this

I would start with a compression test to see if the engine is healthy enough to be worth looking further.

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You don’t say if there’s a Check Engine light and if so what codes.

Is this a recent purchase and what is your normal driving pattern ? if all city stop and go the fuel usage might not be that far off normal. Have you checked the mostly highway MPG.

A stuck thermostat can make a big difference, so that’s one possibility.

… as are spark plugs that are overdue for replacement, tires that are underinflated, carrying needless extra weight around in the cargo area, and–of course–where and how one drives.

I had the same car at one time, and I can tell you that my “normal” overall gas mileage was 23-24 mpg, with long highway drives resulting in 28-29 mpg. If I had occasion to do exclusively urban driving, my mileage could drop as low as 17-18 mpg, but… I maintain my cars meticulously, I don’t tailgate, and I always try to drive as if there is a raw egg between my right foot and the gas pedal/brake pedal.

We have no idea regarding either the maintenance of this car or the way that it is driven.

you would assume the h6 motor which is more reliable would also have no issues with cats due to burning coolant/oil so that might be in its favor. a typical in city/short trip mileage might be 15mpg. i would verify it with a longer trip at hwy speed and see how it compares.

Cavell, Thanks for your feedback. My brother, who owns an 03 Outback said about the same thing. I’m so pleased that Click & Clack’s legacy carries on in this way. Car Talk was the best show on modern radio, in my humble opinion.

Scott Currie, Master Potter

A faulty coolant temp sensor for the computer can cause poor fuel mileage.

If this sensor keeps telling the computer that engine never reaches operating temperature when it actually does, the computer will run the engine in the open loop mode, which uses more fuel.


I will look into that stuck thermostat thing. I am the worst kind of Car owner: I know a fair amount about the workings of the machine but I am a dult when it comes to fixing things. I tried to fix my 1964 VW Bus way back when VW’s for Dummies was all the rage. When I put the engine back together, I had a few pieces left over in my muffin tin parts holder! Not a good thing with old VW’s.

Thanks for your response.

Scott Currie, Master Potter

Thanks for your input. Because the car is new to me (bought last Fall) I have mostly used it for around town driving and going to and from work-6 miles round trip.

Scott Currie, Master Potter

No status lights, well, that is after I had the brakes fixed! Thanks for your input.

Scott Currie, Master Potter

Yes, several other responders mentioned the thermostat thing. It revs fairly high when starting up from a cold start, but seems to calm down after a minute or so. Could that be a sign of something? Thanks for responding to my question.

Scott Currie, Master Potter

The thermostat and the coolant temp sensor are two separate things.

The thermostat allows the engine to reach operating temperature as quickly as possible.

The temp sensor for the computer informs the computer what that temperature is.


I though about that a compression test too but it seems to have pretty of good pep when I put the ‘peddle to the metal’. Thanks for responding.

Scott Currie, Master Potter

Some guess from my own recent experience.
Dragging brake calipers robbed me of 1.5 MPG with no severe side-effects on drive-ability.
Run your car few miles with very gentle brakes usage, then feel hub caps with your hand: if one or two are hot, you might have dragging brakes.

Bingo , we have the answer . Take a normal highway drive sometime and see how your miles per gallon compare to what the rating is. Should be about 27 unless you drive 80 MPH.


Another guess: were tires replaced recently?
I used to own an Outback, which dropped something like 2-3 MPG one I replaced OEM tires with BFGoodrich T/A.
New tires were nice/grippy and much less noisy, but MPG suffered miserably.

We bought a new '16 Outback and it wouldn’t go anywhere in snow because Subaru chose the stock tires for mileage rather than grip. Kind of like selling a rubber knife so people don’t cut themselves.

I see this a lot. Cold weather comes, people do short trip driving and then panic when they see their mileage. You can clearly see what a cold weather start does to mileage when your vehicle has a mileage display and you set it for “trip mileage” meaning it resets itself each time you start the engine.