I did the fuel filter....which was a Delco so could have been original, this weekend. Also flushed the radiator, did the thermostat (also had a Delco 195 in it...might have been origianal..looked it), and changed the oil and filter with GTX 10W30.
Too soon to tell if the mileage has improved. I still get a Check Engine light if I drive any distance at steady speed on the highway. Around town it's fine, no light. Weird.
Averaging 15-17mpg.
-Mike