i myself think that 40 liter is not correct, it has either 26 or 28 liters capacity. and about avg i dont care, for 1 km +/- i will not hypermil or slow my speed. i get 11/12 for speed around 110-120 km / h. i am fine with it. i seriously think avg should only be worried if difference is 4-5km not less than that.
and kuch asay hi log hongay jo one way ki khilaf warzi kartay hain. just because to save few km's in average.