need more mpg help

I have a 95 lesabre 3.8 runs great, buick dealer says computor has no codes or hidden ones, but it only gets 18-21 mpg depending on the octane rating and it is not city driving most of it is 55-65 mph. what are you people out there getting and can I get the same as you?. I do not drive it hard. most of the time the wife has it. any ideas to inprove the mileage?

My '97 on a good day will get about 27 HWY mpg.
Perhaps you are ready for a new set of plugs, fuel filter, air filter and PCV valve? Do you have a brake caliper sticking a little bit - does it roll OK? Recommended tire pressure too? Overdrive not kicking in? Some of these suggestions might be too elementary, but I agree with you that you should be getting better mileage at highway speeds - especially since no codes are pinpointing a problem. This time of year isn't good for mileage either. My car gets lower economy in the winter cause I have to warm it up for so long before driving - and that makes a difference in how frequently I'm at the gas station. What do you others think?
Tom

My 2000 Limited is getting 26-28 on highway, usually 21-23 in town. Sometimes 30 going with the wind. This is checking with the DIC.

I read somewhere that the O2 sensor can affect mileage, and they recommend changing every 60000 miles, but I havent tried it.

i wish i could get better than 24 on hwy in my 97 regal, our 88 lesabre would get 30 on the hwy

It sounds like your Oxygen Sensor is almost DEAD!
The older the sensor, the SLOWER the reading it transmits to the onboard computer, that then tell the Fuel Injectors what to do.

I waited till mine died, and its now fun.

Dead O2: 12 - 13 MPG !!@!! / Slugish performance

New O2: 28 - 30 MPG !!!@!!! / Quick performance

93 Buick Lesabre Limited

You can check O2 with a DMM (Digital Multi Meter)
Your readings should jump between 0 and 1 volt rapidly.
The faster the better performance.