Anyone here driving a six cylinder model?

[2thdr]

I am trying to decide between the two. I have an 04 M3 but owing to more travel in my schedule during the winter months, am planning to switch to a X5.

I was originially planning to get a ML 320 CDI, as the diesel's fuel economy and torque were appealing features. But, and a big but, the MB dealers in my city are phenomenal pricks.

So I am back to considering the X5. But, in trying the 3.0 litre, I had the distinct impression that the engine was underpowered for the size and heft of the vehicle.

Can anyone with a six cylinder model please comment on their opinion on the engine. How about fuel economy on the highway?

Thank you in advance for the information.