First, get that turbo over to a full synthetic ASAP. Before that, you may want to cleanse out the crankcase and turbo lines with an ARX treatment. I would. Your intervals are not bad. But I am now very wary of dealer bulk dino in the P2 turbos, as sludging has been reported just outside warranty on several. And a 5W-30 dino is one of the last things I would put in one.
If price is no object, if it's modded, or you drive it hard regularly, then I recommend Redline 10W-30. The turbo white blocks run terrific on it.
But if price is relevant, then the candidates I would consider (in order) are Delvac1/M1 T&SUV 5W-40 at longer OCIs, M1 0W-40 at shorter OCIs, and M1 10W-30 at average OCIs. All are excellent. Otherwise, note that the white blocks do like 40 weights best and the lighter manufacturer recommendations are more for mileage considerations.
Don't run a 15W oil in these in the winter. In fact, you don't want to ever get too thick, as you will compromise turbo spool up.
And don't scrmp on filters. Either a Volvo/Mahle or a Mann are perfect.
This, from an S60R owner.