2008/2009 are some of the first bluetecs....so likely will have more issues than the later ones, though its also possible all the issues may have been fixed already at this point.

Personally my 2015 bluetec has been 100% reliable. No mechanical issues at all in 10+ months, 8000+ miles of ownership.

__________________
-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)