Mine has been firing up fine and its about -5F here....one glow cycle, cranks/running in less than 2 seconds.

Heck I've fired up my 300SD back in the day at -12F with about 50 seconds of cranking....and my 190d 2.2 I fired up around -7F in about 10 seconds of cranking. A bluetec with good fuel in it should have no issues at all.

__________________
-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)