Help me decide. I need a good oil for MN winters. I am using Chevron now, but they changed there pour point to -33f. It used to be -44f. I was set on the Pennzoil, but saw that it shears down easily, but pours at -44f and pumps -6600 at -30c. The Durablend pours at -39c and pumps at 5400 at -30c.