[stuart bowes]

I do mine the other way around which is arguably less accurate.. every week I let the needle get to start of the red (not as far as the light coming on), put fuel in, then log the number of litres on the receipt against mileage.

so i'm relying on gauging by eye where the needle is, but it's close enough to be reasonably accurate

if you're doing it by brimming the tank then noting mileage when you brim it again, theoretically that's more accurate because you can't over fill it can you

splitting hairs though really - it would only make a difference of about 0.5-1,mpg at worst.. and my 'errors' would average themselves out anyway because I have a weekly average and a cumulative average on my spreadsheet

then again if you don't need a full tank because you're only doing local trips, you're carrying around all that extra weight of fuel which is less economical. saying this if my last journey was anything to go by, these Volvo's don't seem to even notice being fully loaded! I literally couldn't squeeze any more in and it made not one even slightly noticeable difference to handling or braking