The 6.2L Corvette has a 5W30 oil fill cap, but on race days 15W50 is recommended.
Put the same engine in a max-trailer 7,600 lb. GVW 1500 pulling a 12,000 lb. trailer up a mountain pass on a hot day, and all you need is 0w20, according to the cap.
Cut 2 cylinders off the front and make it a 4.3L V6, and the 5W30 oil fill cap from the Corvette goes on that engine.