[MetroMPG]

You probably already know this, but measurements taken during a trip aren't the best way to do this.

You ideally want to: repeatedly drive the same segment of road one run after the other, in the same conditions, with a fully warmed up vehicle, changing only your speed on each run.

That's how to get the most credible figures/results. Minimize the number of variables that could be affecting your fuel consumption to just one: speed.