Looking to stock up more this year (during sales) for more 5w-40 for 6.7. Ford list shows Valvoline Premium Blue Extreme 5w-40 and Shell Rotella 5w-40, which doesn't say CK4 or CJ4. Looked up Valvoline Premium Blue Extreme 5w-40 CK4 and it does have Ford's WSS-M2C171-F1. However, Shell Rotella 5w-40 spec sheet shows Ford's Ford WSS-M2C171-E spec, but not Ford WSS-M2C171-F1. Thought Shell was going to meet Ford WSS-M2C171-F1? What are you guys using in 6.7 for 5w-40? Still have 2 more changes with Delvac 5w-40 CJ4.