i test drove the Xdrive30d and xdrive35d back to back recently...only noticed a slight improvement on power, more so on the initial startup...once you've got the car running on 2nd/3rd gear, its about the same.

i have yet to drive the new xdrive40d and LCI xdrive30d though.

anyone able to share their experience?

Fraser, you are an expert on X5!