Maybe it was best not knowing.
Drove 80 miles and it took 8 gallons to fill back up = 10 mpg
Although, when I got onto I-5 southbound, I got stuck in a traffic jam. Stop and go and 20mph. I got off I-5 at Salem and came back up Hwy 213. Filled back up in Mulino. So, it's tough to say.
So much for my experiment.