Hey Wise I gotta say just by going to the diesel you should experience better mileage if not the same......but consider that the diesel truck you buy is most like going to be around 1000 pounds heavier. Consider that in my 1995 Chevy XC SB z71 on 35" tires I averaged around 12-13 at best. The truck weighed a bit over 6000 pounds. My PSD is a CC LB and has 35's on it too, and weighs around 8000 pounds and gets about 17-19. I know the Titan has more advanced gas engines but still, you won't find the low end torque and towing perforance in them. Just throw a programmer on a diesel and you get an extra 100+ HP and 200+ TQ! In a gas - 30 and 50 if you're lucky!