I checked the oil level of a diesel and there was no show of oil on the stick. 
But this van has a stick that is built into the oil fill cap too, so one does not have to open the engine area.  On that stick it was ok, but it is obviously a home made thing.
I checked the back of the Bentley and it says 4 quarts.  And less if the filter is not changed.
I had to put in more than four to make it to the top of the mark of the factory stick and there was plenty in there already.
I have a Golf with the same engine and it is not as slanted as the one in the van.  
Anyone knows about this subject?
Zoltan