In the older post at this link, I have given the strength of the transport groups in Greece on 5 December 1941. I have now come across some further info on what these planes achieved.

On 6 December 1941, 60 planes arrived from Greece, Tatoi and Heraklion, at Derna between 0742 and 1140, i.e. one plane every two minutes. These planes carried the following during the day:

• 57,000 ltr of B4 to Derna
  
• 2,000 ltr of Rotring (engine oil – see this link)
  
• 2 DB 601 E and 1 DB 601 E aircraft engines (one should probably be ‘N’)
  
• To Heraklion, load of 164th Infantry Division, and Rear Party of 5th Mountain Division
• 4,000 ltr of B4 to Larissa for use of fighters flying through to Africa, and 200 ltr of Rotring
  
• 36 men of Res.Flak.Rgt. 806 to Malemes
  
• One plane-load of cigarettes from Sofia
  

A single plane could carry 9 barrels of fuel.

My guess is that these planes managed one run a day, by the time they had been unloaded, re-loaded, returned, and loaded again, and serviced. There is some reference to planes force landing on the way back due to lack of fuel, which would indicate to me that they were not refueled in North Africa.