'01 OUTBACK BIG MILAGE PLUNGE-WINTER ONLY

[Tom W]

Got an 2001 OBW 2.5 now with 118,000 miles. Now in its 4th winter. Last
year had BIG mileage drop off around December when temps got to be around 40
f. or less regularly. I am talking about a decrease from 25 MPG to around
16 MPG. No change in driving habits. Most mileage is daily 40 mile round
trip at about 70 MPH. Very little stop and go. Have used Mobil 1 since
beginning. Fuel filter, Plugs, Air Filter, PCV, Coolant and Oil all
replaced more often than recommended. Tire pressure is always about 2 PSI
over recommended (cold). Have changed thermostat twice. Heater output is
same as always.

1st 2 years of ownership, this did not happen, just last winter, and now
this. Last year mileage improved around April when things warmed up. Had
check engine light around June that dealer said was Knock Sensor and
replaced. Performance has remained consistent and it starts easy at all
times. No check engine light.

What can cause this last 2 years WINTER ONLY mileage drop off ? I know SOME
is to be expected, but this was sudden and drastic, last 2 years now (BUT
NOT 1st 2 years).

Can it be temp sensor (air or coolant) ? Mass flow sensor ? Suggested O2
sensors to dealer last spring and they said that was rarely a problem
(although I did not leave for service at that time).

Also have burned rubber smell from under hood when I park and get out, for
several months now, that I cannot trace. Now occasionally smell it inside.

Any help greatly appreciated.

Thanks,

Tom

 

[Greg]

Here in California we get winter "oxygenated" fuel but this only usually
accounts for about a 1 or 2 mpg drop.

 

[Edward Hayes]

Give us more information like how long since a tune-up and especially spark
plugs and air filter. Have you used a fuel system cleaner like TECHRON FUEL
SYSTEM CLEANER (walmart ~$ 6). Have you made any other changes like putting
on oversize tires etc? ed

 

[Michael Prosek]

I just bought a WRX so i dont know much about subs, yet. But i use to have a
Ford Probe GT awhile back. The car had 2 O2 sensors. I had that same burning
smell. I cant remember haveing a drop in MPG but the car ran fine, no CEL
except sometimes when the smell was present, but it would go out after a few
min. I let it go for awhile cuz i didnt know what could be causeing that
smell and CEL, belts , clutch maybe ..seemed to happen when i would get on
it hard. After reading some message boards people told me to replace the
front O2 which was a common thing to go on those cars. I got a bosh
universal one since the ones made specificaly for the car where more
expensive. The smell never came back. The car had less then 75,000 miles
when i started having that problem. I would tell the shop to check it.

 

[CompUser]

Got an 2001 OBW 2.5 now with 118,000 miles. Now in its 4th winter. Last
year had BIG mileage drop off around December when temps got to be around 40
f. or less regularly. I am talking about a decrease from 25 MPG to around
16 MPG. No change in driving habits. Most mileage is daily 40 mile round
trip at about 70 MPH. Very little stop and go. Have used Mobil 1 since
beginning. Fuel filter, Plugs, Air Filter, PCV, Coolant and Oil all
replaced more often than recommended. Tire pressure is always about 2 PSI
over recommended (cold). Have changed thermostat twice. Heater output is
same as always.

1st 2 years of ownership, this did not happen, just last winter, and now
this. Last year mileage improved around April when things warmed up. Had
check engine light around June that dealer said was Knock Sensor and
replaced. Performance has remained consistent and it starts easy at all
times. No check engine light.

Oxygenated/winter fuel used where ya live?

Leave the defroster on, full time (with AC
compressor running, by default)?

I'd suspect drop in tire pressure with cooler
temps, but ya said that was covered...

 

[Tom W]

Give us more information like how long since a tune-up and especially spark
plugs and air filter. Have you used a fuel system cleaner like TECHRON FUEL
SYSTEM CLEANER (walmart ~$ 6). Have you made any other changes like putting
on oversize tires etc? ed

MORE INFO ON WINTER ONLY GAS MILAGE PLUNGE.

No alterations to vehicle (tires or any) Techron used monthly. Plugs
changed every 30,000. We do not have Oxygenated fuel in my area. Tire
pressure about 2 Lbs more than factory spec (cold). Defroster not run much,
and compressor won't run under 40 or so degrees anyway. All filters and
other maintenance done MORE OFTEN than recomended

****NOTE**** THIS DID **NOT** HAPPEN 1st 2 WINTERS I OWNED IT****

Any help greatly appreciated.

Thanks

 

[Edward Hayes]

Sounds like you have done the maintanence and no check engine light so I'm
thinking your O2 sensors maybe getting tired.

 

[Edward Hayes]

Another thought is that the O2 sensor has a pre-heater which if bad will not
cause a CEL in earler versions.