Having had 2 Kia Sorentos, 1. manual & 1. 5 speed auto.
I can safely say that the difference in average fuel consumption was 8 mpg 33mpg manual, 25mpg auto. However, I have recently had an update done on the cruise control which appears to have improved the return. since this has been done I have only use 1 tank full so I am unsure if this was a one off or a permanent change.
Steve W
A copy from the post below