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Guest Message by DevFuse

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mpg decline

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10 replies to this topic

#1 brompy


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Posted 18 January 2004 - 12:36 PM

just posted a message in the wrong place so i will try again

first time on here so bear with me

have 2000 legacy outback....had it since new
has 111,000 miles
had mpg prob 2 yr ago and was told nothing was wrong .....when i got home from the dealer i had a recall on the O2 sensor......fixed the prob.....but has been slowly declining in mpg for awhile.......did a tune up and put new bosh plugs in and K&N filter.......lost 3mpg........Just got done replaceing my leaking head gasket and put a std. airfilter back in to see if that would help .....didnt do much...........anyone have any experience or ideas

#2 northguy


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Posted 18 January 2004 - 12:45 PM

I guess I wouldn't be too alarmed about 3 mpg given that the air is considerably colder /heavier in the winter, thus longer warm-up time, less efficiency burning, and more idling time before you take off. Also, the additives in gas in the winter (ethanol and oxygenated fuel) tend to reduce their efficiency also. But, keep an eye on it to see if it continues to slide.

#3 Nuwan


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Posted 18 January 2004 - 02:02 PM

during winter months gas companies switch do different winter grade gas, which has more detergents and gas-line antifreeze in it that tend to lower fuel mileage... things should look better in the summer months

but don't neglect the simple things, ie; tire pressures... have you changed your tire brand/size recently? winter tires and wider tires will effect your mileage as well

good luck:D

#4 intrigueing


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Posted 18 January 2004 - 03:51 PM

Like others said 3 mpg in the winter is not a big deal, however if you can change the plugs yourself - subies tend to like NGKs better. What MPGs are you getting? Have you been driving in different terrain or snow? Running a compression test can't hurt either.

#5 newsooby


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Posted 18 January 2004 - 09:50 PM

Brompy, do you recall what year vehicles were effected by this recall?

I've got a '99 with declining MPG -- I suspect the O2 sensor -- and I've been looking for info to see if there was O2 sensor recall for '99s.

Can you send me a URL to the information?


#6 brompy


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Posted 18 January 2004 - 10:24 PM

if i recall it was in late 2000 or early 2001 ......my car was purchased in march of 2000......I dont know the extent of the recall and I was informed by mail.....I still believe that it is an o2 issue for fuel milage.....but the cost of getting a new one is prohibative.....I was told 500$

#7 99obw


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Posted 18 January 2004 - 11:00 PM

If a dealer is quoting you $500 for an O2 sensor find another dealer. Maximum I think a dealer should charge would be $200. The part lists for $120.00 and it should take no longer than 1 hour.

I changed the front O2 sensor in our '99 for about $50. It's very easy to do.

I would replace the plugs and air filter with OEM parts and go from there.

#8 northguy


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Posted 19 January 2004 - 12:23 AM

WOW! That's ridiculous. Really, find another mechanic.

#9 subyroo


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Posted 19 January 2004 - 12:56 AM

If you are servicing the car yourself then you need to have the dealer run the Subaru Carbon Cleaner or whatever they call it, it is dispensed into "a" intake hose, I do not know which one, but it sure gets rid of a heap of crap out of your engine.

That would be my next move.

#10 jimkup


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Posted 19 January 2004 - 08:45 AM

Did you try a compression check on the cylinders? My subie had similar issues & found that there was a prob w/ valves or something in head @ #3cylinder. Replaced with rebuilt & solved problem. I only had about 65 psi in the one cylinder that should have been about 155 psi.

#11 meep


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Posted 19 January 2004 - 09:46 PM

old timing belt?

clogging cat?

crinkle in exhaust pipe?

Top end cleaning?


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