Ours don't seem to have an issue with that.....my dad's SD has sat for months before and it started and ran instantly with no issues, like it had only been off for a day! Same for the 300D, it sat in the garage 4.5 months and fired up/drove away without complaint....we didn't even have to touch the battery!

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-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)