2005 Subaru Outback Terrible Mileage

[natejj]

I drive a 2005 Subaru Outback 2.5XT, with about 190k on it. Now, this car is AWD, Turbo Charged, and takes premium, I don't expect amazing fuel mileage like my old civic. I do mostly city driving, short trips (less then 5 minutes) and my ride to work is 10 KM on the highway. My car computer says I'm getting 10-12 MPG on average, and I usually get 170 miles from my 52 litre tank of premium

I don't have a garage, so it's kind of hard for me to do any work myself, but I'll be driving to Calgary in the future and can tear it apart with my dad and try and fix whatever is causing this abysmal mileage. Can anyone give me a list of things that I should start with? Oil Change, sparks plugs, air filter... after those easy things, what should I start checking? The 02 sensor maybe?

Appreciate any advice.

[Twin_Cam_Turbo]

You can also see if your tires are low, could be a contributor to the poor economy. Check your oil level. Has the timing belt been changed by now?

[ArjayAquino]

Try cleaning the MAF sensor as well. Ref.

And maybe seafoam.

[ercchry]

is it boosting? i had a break in a vacuum line on the truck and the wastegate was always open... it was a bit of a pig on fuel then

[Twin_Cam_Turbo]

Originally posted by ercchry
is it boosting? i had a break in a vacuum line on the truck and the wastegate was always open... it was a bit of a pig on fuel then

Good call, a vacuum leak could cause poor economy and make it run poorly.

[natejj]

Tires are brand new, and the timing belt was done at 170k. I'll look into the vacuum line, thanks for the tips.

[DeleriousZ]

I dunno if I'd call spark plugs easy on a subaru lol.

As you mentioned above, all the basics like filters, plugs, plug wires, fluids.

Have you noticed any performance issues since the poor mileage started?

No check engine light codes? CAT isn't plugged? No dragging brakes?

[revelations]

Definitely eliminate the easiest:

air filter
spark plugs - check colour as well
tire pressure
find out what REAL WORLD mileage is supposed to be for that year model

Youre not even warming up the vehicle properly by driving 5 minutes - so dont expect great mileage to start.

Make sure you change the oil regularly as this is the single hardest thing on an engine (driving cold).

[SkiBum5.0]

Seems early but perhaps the catalytic coverters? I think the o2 sensors would throw a code for this issues though.

[Twin_Cam_Turbo]

If the converters are plugged I dont know what code would set, but if they have failed they usually set P0420.

[JBreaks]

Man the list is huge.... you should be getting about 400 km's for 50 L premium on that EJ20T

-All ignition components, plugs, wires, ignitor, distributor ect. (but will usually have hard start of misfire in higher rpm)
- Vac lines anywhere (suspect line to wastegate or fuel pressure regulator)
-o2 sensor reading constant lean
-air filter or throttle/manifold clogged (but won't casue that severity of decrease)
-check/clean MAP or MAF sensor
-Some kind of sensor massively retarding timing (Crank/Cam angle sensor, TPS, assuming timing correct to begin with)
-Coolant temp sensor reading permanent cold
-Clogged Cat converter (usually happens due to over rich tho...)
-Massive blow by due to low compression
-leaking capacitors in ECU messing everything up.

there's more.

[Twin_Cam_Turbo]

Originally posted by JBreaks
Man the list is huge.... you should be getting about 400 km's for 50 L premium on that EJ20T

-All ignition components, plugs, wires, ignitor, distributor ect. (but will usually have hard start of misfire in higher rpm)
- Vac lines anywhere (suspect line to wastegate or fuel pressure regulator)
-o2 sensor reading constant lean
-air filter or throttle/manifold clogged (but won't casue that severity of decrease)
-check/clean MAP or MAF sensor
-Some kind of sensor massively retarding timing (Crank/Cam angle sensor, TPS, assuming timing correct to begin with)
-Coolant temp sensor reading permanent cold
-Clogged Cat converter (usually happens due to over rich tho...)
-Massive blow by due to low compression
-leaking capacitors in ECU messing everything up.

there's more.

It probably has the EJ255 not an EJ20, my EJ255 powered Legacy GT would get 400-600km 55L depending on how it was driven.

[revelations]

OP just to clarify (stupid imperial system throwback) ,,, you mentioned 170 MILES in your original post for tank range, but you also mixed in KMS as well with your numbers ....

Was that a typo? Or did you mean 274km with your tank?