I just finished do a tune-up (spark plugs, spark plug connectors, O2 sensor and air filter). As expected the fuel efficiency increased from 22 mpg to 25 mpg. This is 75% highway driving. Is this what I should expect? I think its pretty good for a 230 HP car that weighs 4000 lbs. Sean Sean Douglas 1997 Audi S6 1990 Audi 90Q20V Surrey, BC Canada