Drastic reduction in MPG

It is a 1994 3.0 wagon with 169,000 miles. Within the past 3 weeks or so my MPG has gone from about 26 to 20. A vacumn leak was fixed but have not noticed any difference. Replaced PCV valve also. Regular oil, filter and air filter changes and tire pressure is fine. Original tranny with a recent service. No fuel leaks or thieving neighbors. Any ideas? Thanks

Any codes? Changed plugs?
You might try pulling the battery cable for 30 minutes (some say less) cycling the key to start a few times, replacing the cable and taking a good long run of highway and then city driving. Let the computer relearn.

Is the engine currently running cooler than normal? If so, the thermostat may be stuck open. This is not a good thing for fuel injected engines.

i would change plugs, wires, cap, and rotor this should help out. did for me. then open it up.