The difference in MPG so far has been 0 between my 335 (sitting in my driveway) and my M3 (sitting next to it). They both cost me pretty much 0 to maintain to 50k. Only thing I pay for is mods and since there are so many available for the 335 I guess I am better off with the M3. Also got the E90 M3 as the 335 is E92. Again, more practical. If you think about it, the M3 is almost Prius like in its practicality
