Details in sig, life of the truck (30,300) miles 16.83. Last year in 11 I averaged 16.97. I do a lot of highway/rural driving. So like 85% hwy and 15% city. I drive about 5 mph over the limit pretty consistently. (3.55 LS Rear)

Best I have got is around 19 and worst is about 14.5.

 

First of all I would stop buying 93 octane fuel. You truck does not need it. Your fuel mileage is most affected by driving habits and the way your truck is set up. The gear ratio will be one of the contributing factors to the fuel mileage. 13 mpg is on the low side of fuel economy of late model F150 even with 4x4. Find out what the differential gear ratio is and cut back on the octane.

I lived in Germany many years ago and they had some very good gasoline performance wise. Sometimes even change brand can make a little difference. One of the thing I've found that contributed to better fuel economy is running the tire pressure on the high side of the specifications. If it is like it was when I lived in Germany, you generally have to drive fairly fast on the autobahn to not get ran over by the locals. Stay in the far right lane.