Correct way to check MPG on VX

[Coconut Sunrise]

ok i know the basics of MPG.....However to top off a VX takes some skill
doing at the pump is not the way since all fuel pumps not the same
some I can trickle the fuel and some I cannot. the only way I get a true Top off on level ground is with small funnel and a a graduated cylinder. which is a pain when you are doing a full tank.
The vx fuel tank Neck holds some fuel and unless you shake car to get air pockets
out your MPG will vary.

when I use the same pump and same fuel stop I get numbers all over the place driving the same daily route,

so just what tactics do you guys to get your numbers

coconut