If you can get some oil samples into your freezer, you would know what I mean. I suppose the Pento 0w-30 is a thicker Euro 30 weight and will easily carry the needed HT/HS (hightemp/highshear) rating of >3.5cP for Euro specs. Very much a safe call. MaxLife synth 5w-30 falls into that thick 30 catagory, if that is easier to obtain. I was suggesting a thin American 5w or 0w-30, if you see extreme cold, but a Euro 30, like I said, is a very safe bet and is prefered for winter.
As for the lines, I would assume that you have the small or "normal" lines. I don't know details about it, just to make you aware of this issue.
One appraoch would be to use the same brand of 5w-40 and 0w-30 for summer and winter, like your Pentosin. I think the Euro oils are generally overrated, with the exception of German Syntec 0w-30, which would be my 1st and last choice for a 2.7tt. You did not mention GC as an option, but I will go ahead and do that. AMSoil is another good idea too. Their 0w-30 makes good HT/HS.