Given the additional cost of the diesel engine over a gas engine, the fuel price difference (diesel more expensive), the added diesel maintenance cost and the DEF solution needed for the new diesels the payback when looking at increased fuel mileage the diesel engine will provide to you means you will have to drive ANY diesel truck over 250,000 miles to break EVEN when compared to the a gas engine in the same truck. The real consideration should be the load you will pull and even more important have to STOP!
21 years ago when I bought a new diesel truck (still own it and drove it today 193,000 miles) the break even point between a gas and diesel engine when looking at strictly fuel mileage was about 100,000 miles. At that time diesel was CHEAPER than gas, diesel maintenance still more expense and diesel fuel mileage better than a gas engine. The cost premium (extra) for the diesel engine at that time was about $4,200. With many diesel pickups TODAY the diesel engine premium can be twice that amount at over $8500.00!
Having said all that you in NO WAY need a diesel to pull the load you are describing (Fiberglass trailer). You may want one however you do not need one. A gas V8 gas engine and V6 gas engine will be MORE than adequate for your needs. 4 wheel drive or All wheel drive would be a much better option to purchase on your truck than a diesel engine.
"I" like diesel pickups and still own diesel pickups to pull the heavy trailers and loads that I pull. I also have a 08 4WD 1500 RAM crew cab HEMI with 345 HP. All the power you could ever want. It gets 18-20 MPG on the road at 75 without a trailer and 16 MPG with a single car trailer LOADED. I believe that is more than acceptable as far as fuel mileage. Any gas engine in today's world will easily go 250,000 with good maintenance. I can buy a Hell of lot of gas and drive a Hell of lot of miles before coming anywhere near the break even on a diesel truck versus gas and do so just as comfortably, safely and economically as any diesel truck.
So this brings the question "I" think you should consider:
Will I keep & drive this new truck I purchase at least 250,000 miles?
If your answer is TRULY YES then consider the purchasing the diesel. If the answer is NO buy a gas truck!
Several other questions you should consider:
Have YOU ever driven a single vehicle you have personally owned 250,000 miles? If NO what makes you think you do so with this new diesel truck? How many YEARS will it take you to drive this new truck 250,000 miles? 10 years? 15 years? You will put the most miles per year on your new truck in the first 2-3 years of ownership. That's the way it always works. Are you going to be a "Full Timer" for the next 10 years?
ALL the new trucks/cars built today are far more reliable than vehicles built just 10 years ago. All new vehicles also can experience a mechanical issue just like vehicles built 10 years ago.
With such a LIGHT
load to pull your choices for a comfortable and SAFE towing vehicle are almost endless in today's world. The diesel versus gas discussion is a neat topic that will be debated forever among those who actually pull a HEAVY LOAD. "I" think it's a moot point in the discussion of choosing a pull vehicle when a fiberglass trailer is the "Load"!