Inline 6s get excellent proven fuel economy when tuned right. My 2011 528i has a 3L Inline 6 engine paired to an 8 speed auto and I get a consistent 30MPG driving on the highway. This is a 3900 pound car and the worst fuel economy I can manage driving like a complete fool in the city is 21MPG. Inline 6 engines make a lot of linear torque from a very low rpm meaning youll find yourself rarely ever revving the car past 3000RPM because you just dont have to.
Yes a 3.7 probably wont give the average consumer the sort of fuel economy they are looking for, but a 3L will without a doubt while providing better refinement and a smoother sound over any 4 cylinder you can think of. Plus for the amount of power a 3.7 will put out, youll be getting g
