Mobil 1 is much easier to procure. You can't get Delvac in quarts, since they expect it to be put in differentials with capacities in gallons.
2002 Ford Crown Vic PI 207k, Ex-Kootenai County, ID Unit #42
Down for engine swap
2003 Ford Crown Vic PI 75k
Castrol EDGE HM 5W30, Fram XG2