Fighting to barely get above 35mpg

+1
I was about to post the very same thing, and totally agree.

I think the variable fill bladder in the Gen II in the States can be largely blamed for the perception that the MDF is inaccurate. I think, with the bladder, I would believe the MFD over manual calculations, TBH, bearing in mind that it is 2-5% over optimistic.

Having a Gen II with a solid tank, I get very consistent results, albeit a bit optimistic, with variation attributable to the reasons Uart mentioned.