I pull a 3500# boat and 2500# Airstream with my 2008 X5 4.8i. My mileage with the boat is just north of 10 mpg. Just north of 11 mpg pulling the Airstream. The X5 pulls both effortlessly, but I too notice and fight with the transmission wanting to hold gears too long. On level terrain, it is fine. On hilly roads, I too manual shift.

The smoking issue is probably due to valve steam seals. My X5 is at 107k miles and is beginning to smoke (oil) after prolonged idle or when struck in traffic. I have already performed valve stems seal replacement on a BMW V8, so I have the tools and the knowledge...still not looking forward to the very arduous task.

I installed the BMW hitch and wiring harness, but my X5 does not guide me to the trailer tongue. All it does is turn off rear PDC when the trailer wiring is connected. Is this an iDrive setting I don't know about?