The flow properties of a synthetic 5w30 are very similar to a conventional 5w20. As long as u are using synthetic ur engine will be extremely happy. If u wish to run a conventional 5w30, then i would only do that in summer, but synthetic 5w30 is great to run all year. for example, do a google search for Pennzoil viscosity
and look at the cold MRV etc and compare synthetic tables and conventional tables and you will see what i mean. the engine does not read what is on the label, the engine only knows the physical property of the oil, and the physical cold property of synthetic 5w30 is a match for physical cold properties of conventional 5w20.
Once the oil is at operating temperature, the difference between
cSt of 8.5 vs 10.5, to an engine, means absolutely nothing, a very very minor change in viscosity that will mean the difference of a tiny fraction of a mile per gallon.
WalMart does carry the SuperTech 5w20 synthetic in jugs, and that is what I would use in the winter, for PHENOMENAL cold performance.
The PP 5W-30 wouldn't hurt anything. But they do have 5W-20 PP in jugs here in the states I believe. I see you're near Hamilton and could always perform a cross border raid.
And Motorcraft syn blend 5W-20 is also excellent. Is that available?