interesting thread, can't recall spotting this one.
My old sube is bizarre with highway too...
3600=92mph, and it is in absolute tippy toe on the throttle heaven...bouncing around 30s mpg with a sucking hole in the top of the tank (it used to be in the 40s there). I am from 87-92mph with a sucking hole... it is mythologically hilarious.
the m3 is no surprise with a deep overdive on a power to weight ratio that is quite high.
I like the route of faster and hyper mile. That is the ultimate is it not?
A giant lesson is deciphering a tractor trailer...they are the same all the time, weight and speed. If the engine is content at spoeed, lean games can play and not hurt.