I would love to conduct this experiment but the vehicle has been running with the E38 Fan and clutch set ever since I have owned it. I would have to purchase another fan the X5 4.6is fan and then install it with the 4.6is clutch fan. I can tell you that my temperatures have run really well for the 4.6is with the E38 750IL clutch fan because the electric fan has not had to run high in the summer months and the temp needle has always been at half or slightly less. During the summer months at 100+ degrees the electric fan has not revved up nearly as high as the electric fan on my 540it wagon at the same temperatures so I have come to the conclusion that the E38 750IL fan and clutch is a nice mod over the original. Like I said before I just stumbled across this since this is what was installed in the vehicle prior to my ownership and now I am just changing out an old clutch fan. Just to add more credibility to this over thanksgiving I went to my parents house in Florida 3500 miles round trip and we ran the X5 between 80-85mph and the temp needle never went over half. Most of the time trip the temp gauge was just a little below the halfway mark. By the way the X5 was loaded down with 4 family members, our luggage and the Brembo calipers with new rotors in the back to be taken to my friends machine shop in Miami (for the next upgrade). I completely overhauled the cooling system at the time when I did the timing chain, guides, and tensioners and the only thing I didn't change was the clutch fan. It was still good. I have to believe that the 11 blade fan is better at air distribution than the 9 blade. Furthermore the 11 blade fan and clutch fan is for the V12 engine so I can't imagine that its not enough if not better for the 4.6is.