Gas milage for a diesel / gas engine

I don't have a Fifth Wheel RV, but I have a 34' Goose neck Horse Trailer with living quarters - weighs between 13000 to 14000 lbs depending on how much water and how many horses on board. Pulled this trailer with a 2006 F250 6.0 diesel with 3.73 gears getting an average of 10 to 11 towing it and between 15 and 17 not towing - averaged 13.6 mpg hand calculated over 101000 miles over 7 years - traded it for a 2013 F350 DRW with a 6.2L gas engine with 4.30 gears - only have 17000 miles so far but towing same trailer I average 8 to 9 towing and 12 to 13 not towing - overall hand calculated mpg has been just under 11 on the gas engine. I went with the gas engine this time due to the initial cost of the diesel is now $8000 plus higher maintenance costs for oil, fuel filters (gas engine has lifetime fuel filter!)and DEF, and with diesel averaging approx. $.50/gal more, I just couldn't justify the costs going with the diesel - I figured for my usage, it would have taken between 150000 to 200000 miles just to breakeven on the extra initial cost and higher maintenance cost of the diesel over the gas engine which would have taken between 10 and 14 years to breakeven, assuming no major issues with the diesel which was way too long. Now if I towed 80%+ of the time, the numbers may be different. Diesels are just not what they use to be with all of the gov't regulations they have put on them plus the manufacturers don't stand behind them like they use to - I've heard too many stories where dealers would not cover diesel repairs under warranty these days. I loved my diesel but don't miss the problems that were starting as I approached 80000 plus miles - the gas engine with the 4.30 gears pull my same trailer with no problems - you just have to get use to the gas engine reving up to higher rpm's than a diesel. Hope this helps.