Personally I think you're being ridiculous as you're going to use the fuel regardless of whether the tank is full or not, so you might as well top it up every time you go to the station as it'll cost you the same either way in the long run and you son't have to fill up every few days...
You could argue that running around with less fuel makes the car lighter and so gets you better mpg, but seeing as a 60 litre tank of deisel will weigh about 48kgs it's like carrying around a small child - which in a car that weighs over a ton and a half isn't really going to make a huge difference...
Bookmarks