230k miles, 31.5 mpg as of last week, mostly freeway.

Stuff to check for good fuel mileage:
02 sensor
grounds
fuel injectors
plugs, wires, cap, rotor
tire pressure
air filter
clogged cat
vacuum leaks
pcv
coolant temp sensor/thermostat
clean throttle body/IAC

Anything that would keep the ecu from going into closed loop and basic tune up stuff.