

And the now obligatory standard blue chu photo:

EDIT: here are the actual measurement differences:
rear opening | narrowest point | to driver seat | diag to windshield | passenger height with seats down | passenger door opening to folded seat | |
2015 c-max | 37 1/2 x 28 1/2 | 36" | 66" | 118" | 33 1/3" | 30" |
2008 m5 | 41" x 33 1/3" | 40" | 67" | 122" | 34 1/2" | 30 1/2" |