Hello everyone. My '90 Regina-equipped 740 wagon seems to be way too thirsty. I do mostly city driving, but I'm quite conservative, and yet I am managing about 12-15 miles per gallon. This is what I've done so far:

I examined the engine temperature sensor and found the harness was pretty much shot, so I replaced it. Changed out the spark plugs and made sure they were correctly gapped; unbolted the catalytic converter to make sure it wasn't plugged; changed out the air filter and cleaned the airflow sensor; replaced the 02 sensor with a new one (made sure it was the Regina 3-wire one); replaced the fuel pressure regulator, and run the self diagnostic multiple times (no fault codes).

What should I turn to next? What else could have a significant effect on mileage that I haven't replaced or checked already? Any help or suggestions would be welcomed. I'm living off student loans, can't afford to burn up this much money on gas! Thanks.