Found this recently. More data to add to the pile, from the
web site of a BMW 318ti owner who tracks & posts his fuel consumption.
Note, it's got an automatic transmission.
The plot with solid dots = average fuel economy captured at various speeds on two-way runs.
The hollow dots = actual fuel consumption and tank average speed (also reported by the car's onboard computer).
There's some more discussion of the results, plus metric & imperial graphs on the web site:
http://www.randomuseless.info/318ti/economy.html
