OP - Douggy,
You wrote the dash (135k) & digital (270k) mileage. What were the hours readings?
The hrs/miles average is pretty good at 135k. Unless you overpaid, 245k w/ 9100hrs is better, in terms of wear per mile or for burning off all the fuel particles. Most buses with <150k would have 9000 hours. More starting stopping. You may have another 200k to go.
9k/160k = 17.7 mph avg.
9.1k/245k = 26.9 mph avg.