Subaru - sudden drop in gas mileage

[nekokage00]

Hi. I have a '96 Subaru Impreza with 220,000 some miles on it. I keep
up on it's regular matience and it doesn't seem to run any different
than it ever has. Recently though I have experienced some drastic loss
in gas mileage. I went from getting anywhere from 25-27 then down to
22 then 20 and now when I drove back and forth to work (only about 10
miles) I can actually watch the gauge go down. What is the problem?
This has occured in the last month.

 

[djay]

Hi. I have a '96 Subaru Impreza with 220,000 some miles on it. I keep
up on it's regular matience and it doesn't seem to run any different
than it ever has. Recently though I have experienced some drastic loss
in gas mileage. I went from getting anywhere from 25-27 then down to
22 then 20 and now when I drove back and forth to work (only about 10
miles) I can actually watch the gauge go down. What is the problem?
This has occured in the last month.

I experienced a similar thing with my 98 Legacy. Gas mileage was driving me
nuts. Tried the system cleaner fluids and better grade gas/ new air filter
etc. Just last week the CEL came on and the code, P0136 pointed me to an O2
sensor. I replaced it this morning and drove 50 or so miles. And while it
is too early to say definitively, the gas gauge needle seems to have slowed
a bit on its way toward empty. Hopefully that means my poor gas mileage
woes are through!

HTH,

DJay

 

[thomashanno]

Are you possible losing gas? From what I've heard, and experience with
my own 97 Legacy Outback and some friends' cars, the fuel filler pipe
can rust out and leak gas. There's a plastic piece on the bottom of
the pipe that catches dirt, salt, and other road debris and eventually
it causes the pipe to leak. You would probably be able to smell the
gas after you filled up if it was leaking as quickly as you describe
though...also, my gas gauge pretty much stopped working after my leak
started.

 

[Carl 1 Lucky Texan]

Hi. I have a '96 Subaru Impreza with 220,000 some miles on it. I keep
up on it's regular matience and it doesn't seem to run any different
than it ever has. Recently though I have experienced some drastic loss
in gas mileage. I went from getting anywhere from 25-27 then down to
22 then 20 and now when I drove back and forth to work (only about 10
miles) I can actually watch the gauge go down. What is the problem?
This has occured in the last month.

One possibility is the Engine Temp Sensor (not the temp gauge sending
unit). It can keep the ECU in choke mode. Though I suspect with just a
10 mile drive, you're mileage will not be great because ,in winter, the
engine may be in 'choke' mode for a coupla miles anyway.

Carl

 

[Cliff Top]

My own experiences with an O2 sensor somehow getting contaminated/blocked
gave very poor mileage and a noticable loss of power. You had to be very
heavy on the accelerator.... Maybe that symptom matches yours? A
genuinely faulty sensor appears to give worse running problems than this-
like misfires etc
The problem was caused by something in one tankful of gas - performance
dropped off quite quickly over 200 miles~
It took another 5-6 tanks before it finally cleared (deposit burnt off
sensor??) Been fine since.

Hope that might help

Cliff

 

[wrx]

Hi. I have a '96 Subaru Impreza with 220,000 some miles on it. I keep
up on it's regular matience and it doesn't seem to run any different
than it ever has. Recently though I have experienced some drastic loss
in gas mileage. I went from getting anywhere from 25-27 then down to
22 then 20 and now when I drove back and forth to work (only about 10
miles) I can actually watch the gauge go down. What is the problem?
This has occured in the last month.

If you're in the US somewhere in the temperate zone, everyone's gas
mileage has gone down noticably. That's because the winter gas now
contains about 10% ethanol, which contains less energy than gasoline.
Your mileage will probably go up a bit in spring. In past years, they
used MTBE's which affected gas a bit less, but they've been outlawed
now, and for good reason.