I own an 98 S70 with about 117,000 miles. For first 2.5 years put about 900 miles a week on car, mostly hwy, back and forth to work, but NY traffic. Took about six months hiatus, and now do about 550 miles/week.

During the past eight-10 weeks I've noticed my gas mileage has gone from 26 mpg hwy to about 19, and 20 mpg city, to about 14. I was due for a tune-up and some other maintenance items so had all done including: brakes (front and back), plugs, rotor and distributor, timing chain and pump (no comment), fan belt, as well as fuel filter (mechanic said the old one was clogged and thought the new one would fix the mileage prob.). Even purchased new tires (Yokohama a550) It's been two weeks since all that's been done, and still the mileage hovers at those low levels.

Also in the past 4-5 weeks check engine light went on -- twice. OBDII said it was evap code, probably from gas cap not being securely fastened, although I checked each time after the first time light went on.

Is this an Oxygen sensor problem?? If not, what else could it be? Is that evap fault related to mileage problem?

So many questions, hopefully lots of answers. Thanks, Cliff.