The Ford 6.7L Powerstroke v8 Diesel engine uses 13 quarts of 10W-30 oil.
Note the Ford owners manual had a misprint one year saying 15 qt, that is wrong, it takes 13 qt.
In the winter you can use 5W-40.
The oil should be changed every 7k miles or sooner. You can go longer with synthetic oil, up to 10k.
You can change the oil yourself but can be messy.
The engine gets good gas mileage and has had some problems.