How many miles does the 2020 have?I have had 2 expeditions now and mpg has been pretty consistent with both. Most of our driving is short trips in town and doing that the mileage is not great 12-15 but usually more in the 12-13 range. These are not great at short trips around town. MPG has been the same for both I have owned around town.
Thus far my new 2020 seems to get slightly worse mpg on the highway and towing, this is hard to scientifically quantify due to all sorts of external factors but I seem to be consistently about 1mpg less in the 2020 on the highway. I only have about 3k miles on the 2020 so it is hardly enough to make any sort of statement on it. We may still be running winter gas for most of that too.
I will say that I for sure have seen better mpg when using premium gas than lower octane, especially when towing and on long highway runs.
I should follow @LokiWolf advise and replace my plugs with something better. I was about to do that on my 2019 before it was no more.
Also, I see you went from XLT to Plati. There is a good difference in weight there, and unsprang weigh especially. 22's on the Plati weigh more than the 18's on the XLT, and will negatively affect MPG, especially Stop and Go wise. More energy needed to get them moving.