Cookie,
I agree. However, in Ford's testing, some CK oils are not meeting wear standards as of right now or Ford's specs for wear standards due to different "ingredients" in the CK oils. Shell rep is very confident the T6 will pass or meet Fords tests soon (ok few months). For right now tho, he recommended to use the T5 as it does meet Ford's specs/tests. If you want/need CK oil that meets Ford's specs/testing, as of now, seems that Motorcraft is the only approved oil. If you don't need the CK oil, CJ will still do (ie: T6 5w-40). If I was a bettin' man, I think the reasoning behind Shell rep saying to use T5 if you need CK oil is that it has something in it that meets Ford's specs that the current T6 CJ oils don't.
While waiting for this to settle down, I went online to Wal-Mart and Napa to check prices of T6 and rating if possible. WM didn't show the rating and was 21.50/gal (am thinking it's still the CJ). Napa is 29/gal and is the CJ. Was told by Napa that they will be having a sale on Rotella starting tomorrow, but wasn't sure of price--fella is thinking 19-20/gal.
It's to my understanding it's the '17 engines that require CK oil. '16's on back were ok w/ CJ, but rep said if still in warranty to use T5. I thought there would be 2 classes of oil (CJ & CK), but sounds like CJ is being phased out.
But here's the thing. If whatever 6.7 model year you have calls for CJ oil, don't get why the rep would say to use T5 if still under warranty if the T5 is CK rated. My '15 PS calls for CJ oil. Man this is getting more complicated than it needs to be. Ugh!