You're saying tires make a big difference to mpg. I'd read that to mean due to rolling resistance. Am I right on that? But @Prodigyplace , maybe due to some typos in your post, seems to be thinking you're talking about different tire sizes, outside diameters? Again, am I reading that right? Anyhoo, sticking my oar in, lol.
I was thinking different size. Since the OEM tires are LRR I also doubt the review units used different tires.
i was simply stating that with the improved efficiency of gen 3 over gen 2 in my experience, i would expect another gain in gen 4, as the o/p expected. what i meant about the tires is pressures should be check, brand and model (although a 2016 should have lrr oem's, and yes, i do think the larger wheels suck up some gasoline, but i haven't seen definitive testing with way. i'm still confused as to how pre production units play into my post, or the o/p.
OP is quoting his mpg as displayed. I mentioned he should calc, since the displayed is invariably optimistic. This would allow him to more accurately compare to others, say at Fuelly. I mentioned as an aside that pre-production model used by Wayne Gerdes did have a accurate mpg display. I didn't intend any tie in between that and your post, about tires.
he's comparing his '16 to his '04. if he uses the display for each, it shouldn't be off by much. if all other contributing factors are the same, his mpg should be better. doesn't really matter what's going on with fuelly.
As Sam said, just reset it next time you fill up and drive it as normal. You should expect to see worse mpg in the colder months than in summer, so you can't compare your mileage with those from the hot states. The car was designed to run on low rolling resistance tyres so other values will affect your results. Good luck and don't over think it, just enjoy! BTW, time to up your profile to show your Latest Gen 4 now.