I'm just curious because I've never seen an engine drain plug on a Benz that required a Hex bit. All that I've seen have been basically drain "bolts." If you do anything at all, you should have a 14MM wrench that fits.
If you do indeed need a 14MM hex bit, you can get a set at AutoZone with a 12, 14 and 17 for very little. They will be a good purchase, because you usually need the 14 for the rear axle and manual transmission drain and fill plugs.
Is this an aftermarket drain plug?