Well it's a 40 litre tank, I filled the thing up to the top of the neck so I guess another litre? It did 52 miles to 1/4 of a tank so 11 litres. 11/4.54 then 52 divided by that.

It hasn't been serviced for the two years I have been with her but it has prob only done 8k in that time. I'm reluctant to do it because I can't see it making that much of a difference (I don't treat all my cars like this!)