I'd follow DJs suggestions, they're all good.
I would like to add that, in my experience, frequent stop & go trips highlight the inaccuracy of the mpg meter but on long trips it can be pretty accurate.
On a long interstate run where I fill up and get right back on the interstate and cruise at a reasonable speed I'll get in the neighbourhood of 400 miles a tank. On hauls like that the most meter tended to be a couple of miles within the calculations I did using fuel added and distance travelled.
Welcome to NICO!
