Ford recently published an oil chart for 2020. Up to a week or so a go, they still had the 2019 chart posted. I didn't look for differences between the two. I think this new chart is much more difficult to read. I posted the 2019 chart in other thread(s).
Note (4) is for the 6.7L Diesel.
Note (6) continues Ford's worry about insufficient antiwear capability of API CK-4 oils. Shell Rotella T6 5W-40 meets the Ford Spec and is on the approved list.
Note [4]: Check Owner's Guide for appropriate viscosity depending on ambient temperature, duty cycle and biofuel content.
Above 20°F(-7°C) use SAE 15W-40 WSS-M2C171-F1 (except 3.2L Power Stroke® Diesel)
Above -20°F (-29°C) use SAE 5W-40 or 0W40 WSS-M2C171-F1, CJ-4, CI-4 [6]
Above -40°F (-40°C) use SAE 0W-30 or 0W-40 WSS-M2C171-F1, CJ-4, CI-4 [6]
Note [6]: Oils showing CK-4 and CJ-4 in the API Donut are not recommended unless they are approved to WSS-M2C171-F1
http://www.fcsdchemicalsandlubricants.com/quickref/oilchartUS.pdf