Right now I'm running 2 quarts of Mobil 1, 15w50 blended with 4 quarts of M1, EP, 5w20 for my winter run.
No problems for the winter....engine runs fine and the oil flows fast with the oversized K$N filter.
I picked up the oil summer in FL when they were clearing out the Kmart's.
At $3 a quart M1, 15w50, I cleared the shelves at a few stores.