approx 10 days ago mine was empty...was planning on doing the worcestireshire wander run so brimmed it...£59.73 it took!
i reset the trip and im currently on 253 miles with quarter of a tank left...no motorways just usual morning/evening traffic and usually i dont exactly drive like miss daisy as most of us do so im quite happy
as for the shape of tank im presuming it doesnt matter as if brimming it will fill up properly...its only when you get below half a tank and turn sharply does the shape of the tank make a diff...the lower the fuel the bigger he difference
hope this helps
andy