It would be interesting to see if your fe is better at 50 or 55 or 65 rather than 60.
When towing my F150 has a very small sweet spot (as far as keeping the E4OD in OD is concerned) at between 52-55 mph; under 52 and it won't give OD because of the slow speed and load, over 55 and it won't give OD because of the increased aero and rolling resistances. Mind you this is on really flat highway- the slightest rise or gust kicks OD out too. I know when towing OD "should" be locked out but I really like OD, what can I say? Perhaps I am ODing on OD.