I have gotten 16 with my 7.3 eb 4:10s and stock tires driving like a little old lady. Real time I get best of 15 empty worst of 10 (loaded towing about 6000 pound boat, canoe on roof, two bikes in the van and all of our goodies for a few weeks) and driving my normal style "80mph". Normally just pulling the boat or one of the broncos I can get about 13 with normal driving habits. Those are actual mpg's on my 7.3 with 4:10s and 37 inch tires.
Derek