100k is approx 60 miles so 6l / 60 miles is 1l /10 miles.
4.546 l = 1 gallon therefore it's about 45mpg
Those speeds/consumptions look to be off the computer? you can't really rely on that, it's just a guide.
Best consumption will be between 50 and 60mph.
Looking at my recent fuelly fills I'm getting early to mid 40s and nearly all my driving is town
I got 46mpg on my trip from Liverpool to Stonehaven last weekend, thats driving within ALL speed limits ... I have no option