Magirus Deutz FM 192 D 11 FA as WoMo

hello community, I have a question: does any of you know the average diesel consumption of FM 192? I’m thinking about fulfilling a dream and making a WoMo myself to drive with it to bali, tomorrow but not at once… a beautiful 1980 FM 192 firefighter car in top zusatand was offered to me and the space for all family members would also be given there plus the storage room…now the question is you get along with it also in “normal” free or ruin do I care about the consumption of the holiday fund? specified is it according to seller with 18-20 l / 100km, but I can hardly believe that with 9.5 l of space with 6 cylinders… thank you in advance S+