There is definitely a problem with the angle of the vehicle - left to right, when filling up.

My indicated and calculated MPG's vary quite markedly depending on whether the car is on a slope down to to the filler side, or up to the filler side - and it doesn't need to be much of an angle either!

I can get several more litres in when the filler is on the high side...without even realising it.

This is throwing out my calculations by as much 0.5 L/100klm's (5 U.S. mpg)

Has anyone else noticed this?