I was surprised as well. On my trip to Atlanta in July, I reset the mpg as soon as I got on I75. With 2 occupants and some luggage I got 28.2mpg pure highway driving at 65 to 75mph, with a couple traffic slowdowns. I have gotten as low as 18mpg local, in my Expedition. But that was a lot of stop and go and idling in neighborhood streets.4wd, I had a 18’ limited 2wd before this one and it got around 15mpg city. I will say that when on the highway and kept around 70 it gets around 24 mpg but it likes 80 much better . We don’t take a lot of highway trips its all pretty much stop and go short trips that are to blame. A tank does last about a month so no complaints on MPG just amazed at your 21 mpg and yes engaging those turbos to hear the whistle up to 25-30 mph is a learned art that costs mpg.