Originally Posted by Cal Learner

Twice in the past month I've taken 300-400 mile road trips in my 124. Once I got 25.74 mpg, the other time 24.97 mpg. M103 with A/T, no A/C running. Even though they were all freeway miles, some of it was quite hilly, not only flat land. Car has always been regularly maintained, but I just replaced the O2 sensor with about 70K miles on it. Early indication is that the new sensor has improved my mileage by about 3-4 mpg. The last 4,000 miles combined city/highway mileage is 20.51 mpg (mostly before replacing the O2). I'm satisfied.