Earlier this morning I filled up our 2016 Prius v Three in order to beat any short term price increases that might be in the works. Drove 372.9 miles on this last tank and put 7.607 gallons in which equals 49.02 MPG. YAHOO! The car computer estimated 51.5 MPG which in my experience always estimates 2 or so MPG high. FWIW this is all in town driving. The bottom line I am a very happy camper...
Fuel shut offs can vary greatly so multi-fill-up MPG is the thing to focus on. Which is why an app like fuelly is nice.
Just did a 7,000 mile road trip in 18 days, from WI to the SW, of the US hitting 13 states, 11 National Parks. Driving it in the real world (speed limit +5) keeping with the traffic flow. From Death Valley (-250' elev) to Vail CO. (11,200' elev). Fully loaded max payload (2 people with camping gear and supplies for a 2 week trip) cruising at 75 mph when allowed Worst tank 35, best tank 48. 42 mpg average for the trip. . Very happy
I figure if you can achieve some mpg for a whole tank that's not bad, going to be pretty representative. A day or two you might get lucky, but a whole tank is a pretty good leveler.
My experience using fuelly and not the car's calculations is that fuel shut offs can vary the MPG by significant amounts, in my case twice by 15 MPG. Both those times were low 30s MPG followed the next fill up by 60+. While most fillups are a remarkably consistent 41-43 MPG, there are the exceptions. I should also add I tend to fill up at my convenience or when prices are low so any variance is exaggerated by the small amount (maybe 5 gals). Yes, a long day's drive would minimize such a variation and 1000+ miles might make it almost trivial..
