On the F10, it makes a whopping 1 MPG difference. Why bother?
Any fuel savings will be lost to premature component failure.
This reminds me of the V8-6-4 and converted gas to diesel engines that GM came out with in the 70's. The drivetrain was not designed for these kinds of features and they failed prematurely.
I am all for better fuel economy as long as it makes sense. But with modern BMWs constantly having battery drain issues, this makes no sense to me.
2013 VW Golf TDI