Poor gas millage

I own a '02 Subaru Outback wagon. I bought it used in '05 and for the first 4 years it got between 21 mpg (city) and 29 mpg (highway). Or about 340 - 370 miles per tank - when the low fuel light comes on.

However, for the past 2 1/2 years, the car has been getting lousy gas millage. This did not start all at once but was rather a slow decline. It now gets between 16 - 23 mpg or about 250 - 300 miles when the light goes on.

About 2 years ago, after getting the Subaru serviced when the check engine light went on, the millage plummeted. My mechanic could find no reason for this. Since then, he has checked into this problem several times and still can not find the answer. About 1 1/2 years ago, one of the O2 sensors was replaced, with no improvement in mpg. My car is otherwise in top running condition and has been very reliable.

My mechanic feels that this low millage is due to ethanol now added to gas. He said many people are experiencing reduced mpg.

Have any other Subaru owners experienced this reduction?

What are other Subaru owner getting for their gas millage?

Any suggestions?

You did not bother to tell us whether your Outback is a 4-cylinder model, or a 6-cylinder model, nor did you tell us whether it has a manual trans or an automatic trans, but I will try to answer your question anyway.

My '02 automatic trans, 6-cylinder Outback consistently gets 22-23 mpg in suburban/rural driving, ~18-19 mpg in urban settings, and 27-28 mpg in straight highway driving. Its mileage is actually a bit better now than when the car was newer, with the apparent increase in fuel economy happening after ~90k miles, most likely because the engine finally “loosened up”. So, my fuel economy is actually a bit better now than it was, circa '02-'07.

I can tell you from experience that auto trans 4-cylinder Subarus tend to get ~1 or 2 mpg more than the 6-cylinder models. A manual trans 4-cylinder Subaru should get ~ 3 or 4 mpg more than the sixes.

My best advice is to have the cooling system’s thermostat replaced. If it is constantly open, then your engine is running cooler than it should, with the result that it uses more gas than it should. If thermostat replacement does the trick, then your next step should be to replace your mechanic, as this easy fix should have occurred to him long ago.

I neglected to include the following info on my '02 Outback wagon with low mpg:
It is a 4 cylinder and has a manual transmission.
Thanks for pointing this out.

Then, if your spark plugs, O2 sensors, thermostat, etc are functioning correctly, you should be getting something like 21-22 mpg in urban driving, 25-26 mpg in suburban/rural driving, and 30-32 mpg in straight highway driving.