27 mpg is way above average on these gen3's 4 cyl, or 6. I've seen a couple tenths over 19 mpg when towing my 5'x10' utility trailer with a snowmobile at those highway speeds. Never saw above 23.5 mpg with nothing in tow averaging 65-70 mph on one way 75 mile trips. Generally between driving short trips, and longer highway ones, I'm always just above 20 mpg. I always do the actual math, never relying on the truck's. computer led screen readout.....many times its bs.
As far as tires, the firestone's have been decent, but I think there are better choices for an all season tire.