Mine was crap on my GT right after it rolled off the lot (17 miles on the odo). Just under 600 miles today and got 18.4 MPG on the dash (rural highway run @ 60 MPH with the cruise set).
My Mustang had less than 10 miles on it. I forget the exact number but it was around 4 miles. My wife's 2024 VW Atlas had 35 miles on it. The bonus points for that was all the PCM/Modules had been updated prior to us picking up the Atlas.