I would use no additives at all. This thing does not have the old familiar Bosch injection pump which those were meant to lubricate and preserve.

I don't think mercedes has approved anything more than B5 for this engine.

Since your car is tagged as a CDi rather than a Bluetec, I don't believe it is equipped with a DPF.

I recently saw some postings where the direct injection engines started fine without a block heater down to -10F. Down here in Texas it's never even been cold enough to pergola the thing. Just turn the key and go, year round. It's indistinguishable from a petrol car.