They probably confused l/100km with km/l. 8l/100km is quite a common fuel consumption figure (~30mpg). I don't know how they didn't notice this though, because

They probably confused l/100km with km/l. 8l/100km is quite a common fuel consumption figure (~30mpg). I don't know how they didn't notice this though, because most people have a general idea of how often they fill their car and how much it costs.