Ok, I have read some posts here on the fuel mileage but wanted to get some feedback on my specifics.

-95 Turbo wagon Auto and only getting around 20 MPG.
Not ideal conditions for saving gas, since mainly 6-7 miles commute by my wife so I'd guess not fully operating temp on engine-although the gauge shows normal / not low.
But still it's mainly highway and I did do a drive to the airport recently to pick up my wife which is about 35 each way and the average on the dash only moved up to maybe 20.5-21 mpg. (I am using the dash read out fro mileage figures, not manually calculated).
We are in Northern California, so not really cold, been mostly in the 50's F lately.
Not really fast driving or a lot of accelerating, pretty relaxed / normal driving.
First tank was on regular by mistake, but now mid grade gas.

I would have hoped to get at least around 25 mpg given above conditions...

Am I to optimistic or could there be some issues causing less than optimal mileage?

I did tune -up recently (spark-plugs, rotor and cap - wires measured fine resistant), also recent oil change Mobil 1 Synthetic.
Air-filter was not replaced since it looked pretty clean.

Tire pressures ok around 35psi.
No check engine light.

I have seen people here changing o2 sensor for better mileage...is there a way to test the o2 before buying a new one and which o2 sensor affects the mileage, I think there are more than one right?

I also saw some replacing the thermostat...which temp rating to go with from my conditions? My engine temp shows normal

Any other ideas on how to improve the mileage?
--
-95 850 Wagon Turbo (136K) -93 960 Wagon (133K) -68 122 (300+K) [-97 M3 (233K) -69 Firebird 400 (110K) -81Kawi Gpz 1100cc -05 Triumph Speedtriple 955cc] /That's all for now folks :) Lars