My '91 240 automatic had 300,000 miles on it but the previous owner was a close friend who took very good care of everything but the car's body. I drove it about 3500 miles around the West Coast and then home to St. Louis. I kept close track of the mileage which averaged about 27 mpg for that trip.

Then I had it serviced before another 2500 mile trip. My reputable Volvo specialist adjusted or replaced timing belts, plugs, flushed the transmission, cleaned the flame trap, replaced the fuel filter and a few other things. Again I recorded the mileage and it dropped to an average of about 22 mpg.

There are no fault codes although a second shop wanted to sell me an oxygen sensor. The first mechanics have no explanation and want money to look for one.

There's no question that the gas mileage dropped significantly immediately out of the shop. There were no other changes besides a couple of new tires. Should I be thinking about wheel alignment?

I'm stumped.

kjl