£54 fill up is approx 38 litres, which is the maximum I've ever filled up (and I've ran out once). I'm sure the handbook says it has a 50 litre tank? Anyway, 38 litres = 8.35 gallons. If you're getting 520 miles per tank, thats 62MPG. I only get about 420miles per tank which is bang on 50mpg.
Lowest I've ever had from a tank was about 440 miles (52mpg). The most was 554 miles (67mpg). Normally it's between 500-520. Light came on this morning so the computer thinks I've got 50 miles left and the trip is on 489 miles.
According to my handbook, the tank is 45 litres on the petrol and 40 litres on the diesel.