Ok, I checked my milage on the '98 328i.
*In the city driving normal (not racing, but not grandma) about: 23.3MPG
*In the city driving like grandma about: 27.9MPG
*Highway normal guess about: 31.2MPG
*Grandma Highway (cruise set at 75MPH, and driving in flat texas) about: 32+MPG
(haven't finished tank yet, but around 469 and climbing miles per tank)
I have to drive 90 miles to work everyday, so I am into saving fuel! If I have to get around someone slow on two lane Hwy 6, well MPG suffers!