No electric motor installed. And I wouldn't even know where to look. I did forget to mention that I was in ECO mode the whole highway trip, as it does make a difference.
It's a Certified pre-owned 1 owner 2019 with 68000+ miles on it, 3.5L 400hp EcoBoost engine, 10 speed tranny, 3.73 rear end, heavy duty tow, no mods, well maintained, all service records from Ford. I haven't had a tune-up yet.
I'm not sure why it gets that good. But my son has a 2021 Ford F150 extended cab with the same motor and tranny, and he gets very similar mileage as well. I'm actually surprised it does so well. But I take off normal, hardly ever seeing the boost dial go up, always use cruise control and take foot off gas when I see red lights ahead. I use the specified octane, usually from WaWa. Once in a while I step hard on the gas, but most of the time drive it like a luxury car.