Another observation on mileage. We just returned from a trip towing from San Antonio, TX, to Colorado Springs. The entire trip north I got 10.5 to 11.2 mpg towing my 7800lb TT with my F-150. Needless to say, I was very happy camper, thinking that the more I "broke-in" my truck I was getting better gas mileage. However, I was brought back to reality on our return trip home when I was getting 6.4 to 8.5 mpg. Seems that having a strong tailwind vs. driving into the wind does make a huge difference. BTW, my sweet spot towing is 63mph. I was amazed at how many TTs and 5th wheels passed me doing well over 70mph. I pretty sure most had speed rated trailer tires. Wonder if speed had anything to do with the "more that several" RV pulled over for flats?