Lousy Gas mileage

Just bought a 95 PA with 39,000 miles on it. Car is beautiful and runs like a top. No tics, pings or coughs. I love this car and wish I had bought it in 95. However, it's rated at 29 mpg highway, which is 90% of my driving. The best I can do is 24, and more often than not it's less. I don't believe my OBDII is hooked up as it won't comunicate with my testor. This thing runs so well I can't believe there would be something wrong, but it is 10 years old. The only thing that seems a little out of sorts is that it seems to shift too early. Any suggestions? My wife is ready to kill me for getting a car that doesn't get much better mileage than the old car. I haven't changed anything at this point, as I don't want to just replace blind.

Try a new O2 sensor. If it belonged to an elderly person, it was driven on short trips to the market and diner, which kills the sensor. Be sure to check the air filter, plugs & wires also. :iceslolan

I don't believe my OBDII is hooked up as it won't comunicate with my testor.

I have a 94 LeSabre with an OBD II connector but it is an OBD I system. OBD I "A" is pin# 4 and "B" is pin# 5 on the OBD II system. You need a OBD I tester and make up jumpers for the OBD II connector to read codes and test. I hope this makes sense, if not I'll try to do better explaning it. Let me know.