Chill out man

£3.47 in today's fuel money is around 3.47L, so 0.75gal, which is therefore approx. 73mpg, easy

My 300mls to a tank is approx. 22.6mpg
Scientifically (fill up, run, fill up), I get 25mpg.

If you're going to worry about 3mpg, you shouldn't really run a performance car, driving style will make either of those figures swing by at least 5mpg either way

In my opinion, there are seriously thirsty cars (below 20mpg), thirsty cars (below 30mpg), average (below 40), and seriously uncool above 40mpg