I thought I'd run an experiment to test mpg on supermarket fuel (what I normally use) against BP or Shell. I got the tank down to 4 miles left to get as much of the old fuel out as I could and then filled the tank up with Optimax. This was the result.
This is as near as makes no difference $150.
I've been looking recently at the prices of things like the new F10 5 series (which you can get at quite a good price over here) or the previous model 7 series in something like a 730D and its easy to see why these large cars are depreciating so fast here
On a positive note, having driven around for a couple of weeks in the Seat Arosa Diesel, the M5 feels much nicer to drive

This is as near as makes no difference $150.
I've been looking recently at the prices of things like the new F10 5 series (which you can get at quite a good price over here) or the previous model 7 series in something like a 730D and its easy to see why these large cars are depreciating so fast here
On a positive note, having driven around for a couple of weeks in the Seat Arosa Diesel, the M5 feels much nicer to drive