Hmmm, l/100km,
I recently went touring round northern europe, and with 5 on board we averaged 39.5mpg (not that brilliant I know, but it's a petrol car, we had the A/C on, and was fully loaded with a roof box)
Now remembering the formula that "1 mile per gallon = 235.214584 l/100km", we can see that we did 6.03... l/100 km (for 5 perons), or a little over 1.21 l/100km per bum. If I'd used a diesel, I'd be well under 0.9l/100km.
So I think, panda-k-bar, my car doesn't come from this planet. (FYI, It's a bog standard, 1.6l Honda Civic)