once you put on conventional tires its pretty smooth even with the sport suspension. i have a 2008 335xi coupe with continental extreme contact DWS and the ride is very smooth and comfortable. I hate to burst your bubble but you aren't really going to get any better gas mileage with the G. I had a 370z (VQ37HR) and now have the 335 with the 3 liter TT N54... and i get literally the exact same gas mileage.