So you'll drive it 20-plus years at 20-25k miles per year, or 400k to 500k miles? Then there is no question which engine to select. FYI, the 6.7 diesel in the larger trucks are warrantied by Ford for 500k miles, but those engines are detuned in comparison to the pickup powerplants. The biggest long-term expense will be replacing the DPF every 200k miles.

 

I've never had a truck for 20 years. I sold my '89 Ranger in 2001 and that's as close as I got.

At first I was going to say gas (I have both). But the towing, the interstate driving, and the longevity you're looking for makes me think diesel.

Best of luck in your search.

 

Both engines will probably last as long as the rest of the truck.

 

This is always a big debate. Sence you plan on keeping it forever resale value should ne taken off the table.
A gas engine might be better for your driving style, but it's close, as long as you can get those long drives often enough to keep the DPF clean you should be fine with a modern Diesel.
First, no engine will last without proper maintenance, this includes the correct fluids, and changes at the recommended intervals.
If you look at engine hp and torque output between the gas and diesel engines you will find the max output for gas engines will be at more than twice the RPMs of a Diesel engine.
So if the gas engine is used in an application of heavy use, the engine will have to turn twice the speed of the Diesel to get the needed power
So, you have two equal trucks, one gas one Diesel, heavily loaded, so close to max output is needed, the gas engine could have twice the number of revolutions as the diesel. That means the possibility of twice the wear.
Now look at the engine oil, and cooling system capacities. What set up do you think is more capible to handle max loads?
There is a reason that class 8 trucks are almost all Diesel, it's the most economical way to haul heavy loads, this is a place where every penny counts.
If gas engines where cheaper to run they would be using them.
Some fleets are going with gas, but from what I have seen it's because the problems of operators using the wrong fuels and doing major damage. Most u haul type trucks will all be gas. Too meny people where filling the diesel tanks with gas and driving off till the engine dies.causing major damage.
That said. There are some natural gas and propane engines making some gain in popularity, but often that is reganal where those fuels are in abundance and cheap.

 

Barring any out of the ordinary catastrophic failures both will last just fine, but the gas burner will be cheaper to own for 20 years. Only tow 5% of the time?? Gas makes more sense to me. Not showing any preference here, just facts.

 

As noted already, gas or diesel life expectancy is mostly due to maintenance. I put 280K miles on a Chevy Van (5.7 Vortec), much of that towing my 3500 lbs car/trailer combo. The motor went the distance but the van fell apart around the engine. I put 340,000 on a Ford E150 Clubwagon 5.0 gas motor, towing that same car/trailer combo. It was a great vehicle. I did all of the maintenance myself which included LOTS of PM. It left me stranded only once when the fuel pump failed.

As for my diesels; another Clubwagon, this one an E350 7.3 PSD bought with 100+K miles and sold, to another racer, with 350K miles, was faultlessly reliable. It towed a 24' enclosed car hauler for most of that mileage and is still going strong with the 3rd owner. My 6.0 F350 PSD towed the same trailer for 200+K miles. (Traded on the current truck a '17 6.7 F250) The 6.0, with the required upgrades, was a great truck. No issues and was going strong when I traded it.

Gas or diesel, if you do proper maintenance both will provide for a long service life. A gas engine will likely last about half the total miles of a diesel. So where a well maintained gas engine will likely run for 300 to 400 thousand miles a diesel will likely go 600 to 800K, given the same level of care. If you figure the cost to buy either engine you can easily budget the cost of a replacement gas motor at 300+K miles and go another 250+K and still come in under the cost to buy the diesel to go 500+K miles. The cost of maintenance on the diesel will be higher.

I bought the diesel not because I thought I had to have it. I don't tow more than the 6.2 would reasonably tow. Or that it would last longer. I have gotten plenty of life out of my gas motors and haven't kept a diesel longer than any of my gassers. I bought it because its a fantastic engine and mated to the 17+ Super Duty, its an amazing package. And I loved the way it towed. So I bought it to make me happy.

 

Longevity is the same.
Cost is not.
Heavy = diesel
Under 10,000 lbs = gas.

 

I went with the gas engine as i also plan to keep my 2019 until the wheels fall off. Someone on this forum got over 400k miles out of their 6.2 gasser before replacing the engine. The 6.7 diesel is likely designed to last much longer than the gasser. For me.....no way I want to be the owner of a 6.7 when it's out of warranty. To costly to repair vs. the 6.2 gas in my opinion. I only put about 5000 miles a year on my truck with most of that towing 8800lbs so the 6.2 gas made the most sense for my needs.

 

 

 

No way to compare "the way they used to be" on the oil burners. Much more sophisticated with the electronics. For longevity that is a tough question. Twenty years ago would have said oil burner no question ----today flip of the coin.

 

Both engine options will easily last to 400000 miles with proper care. Time is the enemy, especially with the plastic fittings. The solid state electronics actually are very reliable, it is items like coolant lines, seals and pumps that will show their age soonest.

The diesel will cost much more to maintain, and the mechanical aspect will last longer than the 6.2 due to the lower operating rpm and heavier built crankcase. Although, it is interesting to note, it seems gas injectors have a longer service life than diesel injectors, based on my experiences.

 

The 6.7 in the F650 and F750 have a 2 year/250k warranty. No such thing as a 500k warranty. From a fleet perspective we are seeing high 200k's on the 6.7 in fleet service before replacing them. The good news is these engines are far cheaper than the C7 Cat to replace and with the upfront cost being lower it's still a win. We can drop an engine in around 270k and run the truck to 350k before sending it to a RB auction and it still fetches over 30 percent of its original cost.

 

Oops! I was wrong. My bad. https://www.ford-trucks.com/articles...wer-stroke-v8/