made a trip to the in-laws two weekends ago for Memorial Day and had the QX60 in 'sport' mode. I would guess probably about 70% highway, 30% back/side roads for the tank I was measuring MPG (although even half of the highway was under construction and traffic was heavy, so not 'typical' highway conditions, I don't think). Anyway, by the time I arrived at the pump, I want to say the screen was reading like 22.1 MPG, somewhere close to that, which was near as high as I've ever seen it by the end of a tank. Did the calculation by hand to check on the accuracy of this, and hand calculation was 21.4. So the screen was inflated by .7 MPG. Not too far off, but not exactly correct, either.
I believe the PSI in my tires are usually 34-37PSI depending on temp and how long I've been driving on that trip. Quick google research indicates that fuel mileage can increase by about .2% (a VERY slight increase, really) per 1 PSI increase in tire pressure once considering the 'normal' range. so whether I have tires at 36 PSI or 40PSI, really wouldn't amount to much of a difference in MPG at all. I have the upgraded, larger wheels. Probably 20" I think. no tow package, though it does have every other option possible. On this trip we did use the A/C quite a bit, both front and back climate controls were on as we had all 4 kiddos packed in the back. So again, a vehicle this size with my whole family in it, I wasn't necessarily displeased with the mileage. Until I see some of these other posters' information LOL Glad Rooster brought me back to the 'real' numbers so I don't feel as bad about it LOL