Gas or diesel - How much weight and where

[MConnelly]

Wow…that warning was like a traffic cone. Everybody stayed away.
So what the heck I see the post was in October so the original poster is still interested….
Depends on what you are towing . (The Weight) Your budget. Where you intend to tow. For instance if you are towing a 10,000 tag along to the beach on highways a gas rig may do you just fine as there will not be a lot of hill or mountains at the beach.
On the other hand , if you are towing 16,000 lbs and the mountains are your play grounds The grunt of a diesel may be the better choice.
Gas or fuel milage is all over the map.
From my own experience , I have travel friends that tow a 8500lb tag along and love to do the coastal routes. Their tow vehicle is a Toyota Tundra crew cab , long bed. Rig cruises at what ever speed they care to drive and they get 9-10MPG . I believe that truck requires high test . (I Think)
I tow a 15,500lb Fifth wheel. I like the mountains. My choice is a slightly modified 2005 Ram 3500 dually. I can pull any mountain I come across and even in the mountains I get 11-12 MPG.
It is not really gas Vs diesel as much as how much weight and where.
IMHO

[RGene7001]

Certainly, diesel fuel pack more energy to begin with and diesel engine burns it slightly more efficiently, so the mileage is always better with the diesel.
In the not so distant past where transmissions had only 3 or 4 gears and gasengines run out of breath after 3500rpms diesel torque was the real king.
Today it is more about horsepower, ability of the powertrain to multiply input torque and apply it to the ground to move heavy load as well as ability of the engine to provide adequate power and torque over wide range of rpms.
In the case of my TV, diesel and gas versions are rated equally. When it comes to 0-60 acceleration I would outrun diesel ML any day of the week, just because 268hp is better than 210 or 240 hp, maximum uphill speed would be better as well. However, gas engine needs to spin much faster in order to make power. At 65 mph I use 5 or 6th gear, depending on wind and terrain and the tach is at 3000rpm at the 5th, while diesel would be traveling at 7th and turning about 2200 rpms or less.
Would I cho ose diesel if I have to buy a TV now? Probably yes.
Would I trade my TV in for a diesel version? Definitely no!