I can't help with mileage figures but I just drove the 6.0 in a B+ yesterday. I have also driven the 8.1. I liked the 6.0 much better than the old 5.7 (in the B+). If I had bought the B+ I would have got the 8.1 (the 8.1 was a rocket!!) as the 5.7 felt underpowered (to me). The 6.0 feels just right. I own a BT Cruiser with the v10. The smaller and lighter B+ that I drove did feel much like my Cruiser (23' slide) and I didn't feel like I had to rev up the 6.0 to get to the power like I do with the v10. I was very impressed with the 6.0.