[JimD]

Mileage is one of those "how did you measure" things. I keep a spreadsheet on each car and a book to write down each gas purchase in the car. My spreadsheets need updated from the notebooks but I have the first ~23K in my 128i spreadsheet. It is in the mid 30s now so I'm missing a fair bit of data.

But in the first 23K, I averaged a little over 27 mpg. I had individual tanks over 28 mpg and even had a few 3 tank averages over 28. But the only instances where I went over 30 mpg were flukes, I believe. Maybe I didn't fill the tank all the way or something like that. Long term, at least 3 tank, averages are much more dependable than the on-line monitor in the car but that is better than guesses based upon the gas gauge. A single tank average is somewhere in-between. How you fill the tank can make a not insignificant difference.

I don't doubt a 128i can average over 30 mpg but only if you keep the speed down. It won't do it at 80 mph, at least mine won't. I've run back and forth to florida a couple times running just less than 10 mph over and those tanks were not better than my overall average. Dropping the speed back improves the mileage on the instantaneous and I would expect to see it on the tanks if I could tolerate going that slow.