They all have the same 3L straight 6cyl carb engine.
The 13:s and 20:s guzzle way more than the elevens.
I would guess around 20L/100km..
Although some nerds i know persist that when well kept it can run around 12L/100km...
I personally hate the fact that the prices are between 35-50k +vat when i know the DOD sold them at 7-15k vat included back in the day.
30 years old trucks shouldnt cost so much.
Maybe its the fact that off-road freaks pay 30k just for the Volvo portal axels..