Just picked up a 2012 Hyundai Sonata Limited with the 2.4 GDI engine. It has 18,255 miles on it. We live in south central Montana, elevation is 3600 Ft. Often drive over the Beartooth Pass at 10,947 and cruise Yellowstone Nat. Park. The Owners' manual recommends a 5W-20, 5W-30 (API SM / ILSAC...