how much oil does a six cylinder ford 0811 cargo engine ?

Depends on whether you have an oil cooler or not (but not a big difference).
14 litres is what it should take according to the workshop manual but as Wirecutterman says, you can still do it properly by slowly adding oil until level is between the 2 notches on the dipstick. Of course you do need to have a rough idea of how much oil to buy - hence your question - so 3 x 5L containers would be needed.
Make sure truck is on level ground when doing it and of course don't start adding oil until after you've replaced and re-tightening the sump drain plug!! (Obviously)

JD
January 2010

when i don't know how much to put in a vehicle from scratch, i just use a 2 pint measuring jug full and the vehicles DIP STICK then just keep adding and COUNTING and checking on the dipstick put less in as you approach the level mark on the dip stick, when done total the amount of jugs used

wirecutterman
January 2010