I've done some searching around and don't think I have any of the issues offered so far. Here's the details:

98 OBW EJ22 automatic 165K miles

2 years ago go ~26-28 mpg (replaced plugs, PCV/EGR valve, air filter)

1.5 yrs ago replaced plug wires, plugs MPG went to about 24-25 mpg, figured maybe the plug wires were low quality.

4 weeks ago replaced plugs, air filter, ran a bottle of Lucas fuel treatment through it, now down to ~20 mpg

 

Never had a CEL, no codes etc

Car idles and drives fine, no new tires since owning, winter here is mild etc.

Strong gas/running rich smell on start up, typical I know, but seems to have been getting progressively worse.

 

Could be dragging brakes? No brake work has been done since buying the car a couple years ago. I'm going to go jack it up momentarily and see if the wheels spin freely.

 

02 sensor? No codes, but at 165K could be due.

 

Leaky fuel injector?

 

It also leaks a lot of oil from the usual head locations, the valve cover seals are good though, replaced by dealer when they did the timing belt/water pump at 140K.

If your mileage is down that far and you're not getting a CEL, it almost certainly has to be the front O2 sensor. If the sensor was working, you'd get a CEL for the rich mixture.

If your mileage is down that far and you're not getting a CEL, it almost certainly has to be the front O2 sensor. If the sensor was working, you'd get a CEL for the rich mixture.

 

Thanks for the advice, I'm going to check into it. Given the age of the car/mileage, its probably due.

I do not know the quality of the gas sold in Houston but around my home I lose 2 to 3 mpg each and every winter. It does have to do with a change in the formulation of the gasoline. The mileage picks back up around late March.

 

That may be a part of your reduced fuel mileage.

 

Steve

Check the air pressure in your tires?

i have to state this:

Ethanol....

no good.

 

I dont think the newer subaru's get very good mileage in the winter.

My old Tlegs went from 23mpg to like 17 in the winter, then summer again like 23

 

the person who bought my old tleg is seeing same

my 06 is getting only 20 avg now

I'm in agreement with your hunch on the O2 sensor.

 

I would also run some seafoam through your car.

I don't know how well lucas fuel treatment works, but I know seafoam works

very well, and may help remove anything that the lucas may have left behind.

 

Twitch

Thanks for the advice everyone.

Another (+1) for the cold weather. Was getting 26+ this fall with my '97 outback (2.2, new everything), but since the weather has been super cold here lately I only got 16 on the last tank. Some of that is letting it warm up before driving, but when it gets cold the MPG always tanks for me. Was the same way on the last Outback...and the one before that...

The air is colder and denser, so aerodynamic drag is greater. The oil in the tranny and differentials is colder and more viscous. The grease in the wheel bearing is thicker. It all adds up to poor gas mileage in the winter, lots lower than expected from the fuel alone.

I agree on the cold weather too. I went from getting 26-28 this summer in my 98 Legacy 2.2, to 20-22. Changed the fuel and air filters and am getting 22-24 now.

 

Never noticed that big a drop in previous winters, but this year has been a particularly cold one.

Yeah, we're unusually cold here right now too (I'm in Austin, not Houston now) and I just noticed on teh pump yesterday that it may contain up to 10% ethanol. So maybe things aren't as bad as I thought. Still, only 250 miles out of a tank vs 325 or so, hurts.

My 95 2.2l 5sp Legacy drops from 29 to 25 mpg during Salt Lake City winters. Mileage will always drop a little in the winter due to "choke" operation, but I suspect the large drop could be due to a small engine driving a lot of cold gear oil full time.

Edited February 1, 201016 yr by headrush

i too get an average of 29-31 with my 94 legacy gt high roof straight shift.... over the winters its more like 25-26 mpg. of course i can see this happening because on average its 16 degrees night and day here in the aleganey mtns.