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Not sure if this was mentioned (didn't read all the posts)

Whatever I paid for the diesel option (6 g or so), I will MORE than double my return in resale, cost of fuel, longevity, etc. Factor in the other things mentioned, and it's a no brainer. Try accelerating up a mountain pass with a gasser. Diesels aren't effected by thinner air at higher elevations.

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Diesels are also very easy and cheap to modify to make unbelievable increases in HP and torque. A tuner/chip, exhaust and intake will increase your hp and torque by up to 70% for about 1500 bucks.

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It would be a far easier and shorter thread to respond to, by asking "what are the advantages of a gas engine over a diesel" -- Anyone hear crickets chirping in the background? ;-)

Been there, done that.

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Where you want your maximum horsepower and torque varies with the intended use. If you want to go really fast you want high horsepower at high RPM's. If you want to go over steep mountain passes you want more of your power at lower RPM's.

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The arguements of Diesel vs. Gas and HP vs. Torque are far to vague. There are significant differences between the many gas and diesel engines. What matters is the comparison between two specific power plants and their respective power curves. Regardless of whether the engine is fueled by diesel or gas, what matters is does the power plant produce horsepower/torque where you need it.

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As an example, I'll compare what I'm familiar with. The HO Cummins Turbo Diesel with 325 HP at 2,900 RPM and 600 ft lbs of Torque at 1,600 RPM vs. the (more power) Hemi with 345 HP at around 5,000 RPM and 375 ft lbs of Torque at 4,000+ RPM. The Hemi will leave my Cummins behind on the race track, but - hook some weight up behind them and head up a hill and I reach the top first. Why? Because, on a hill, the Hemi will never be able to get to it's maximum HP as it does not have the umphh at lower RPM's to allow it to accelerate in the higher gears. The Hemi, with enough weight behind it, just doesn't have enough power at lower RPM's to allow it to reach higher RPM's.

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Towing side by side down the highway at 65 mph the Hemi will be turning around 3,000 RPM's - well shy of it's maximum HP and Torque Levels of 4-5,000 RPM's. The Cummins will be running around 2,000 RPM's - below it's maximum HP but above it's maximum Torque RPM. As we start up the really steep hill both vehicles will begin to slow (assuming they have enough weight behind them) and the Hemi will move further and further from it's ideal RPM while the Cummins will remain in the sweet spot and cruise on up the hill.

If the hill is steep enough and the trailer heavy enough the Hemi will have to downshift in order to increase RPM's. It will have to continue downshifting until it can hold the higher RPM's. The more the Cummins is slowed by the hill the more Torque it produces and the more likely it is to be able to maintain it's speed without downshifting. Now, to be fair, the Cummins will eventually encounter a hill steep enough or a trailer heavy enough to make it necessary to downshift also but it will take a bigger hill or a heavier trailer to make it happen.

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Most people have towed with a gas engine at some point. Remember the problem of knowing that if you could just get the RPM's up to 3000 you could maintain your speed on the hill. Alas, when you shifted from 2nd to 3rd or 3rd to 4th the RPM's dropped to 2000 and at that RPM you didn't have the power to accelerate. So, you downshifted and the RPM's jumped and you ran them up to 4,000 and then shifted, the RPM's dropped to 2,500 and you began to slow again. You knew you had the horsepower, you just couldn't use it in the higher gears. The diesel experiences that problem to a significantly lesser degree, it has more power at lower RPM's to allow you to accelerate on that same hill, as you accelerate the torque drops but when you shift to a higher gear the RPM's drop back to your maximum torque level again. Put another way (warning: gross generalization) gas engines shift from high torque to low torque, diesels shift from low torque to high torque.

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The same analogy can be used for accelerating from a stop. The Cummins will accelerate faster than the Hemi (when both have a heavy load behind them) because it has more HP and Torque at lower RPM's. Empty, a different story as each has more than enough to move the empty weight of the vehicle - the Hemi will have no problem making full use of it's higher horsepower and will quickly be able to get into and stay in it's sweet spot between 4 & 5,000 RPM.

Generally speaking, diesels produce more power at lower RPM's than do gas engines making them more suited to towing. Gas engines have more peak horsepower making them more suited to going fast. There are always exceptions so make sure you keep the generalizations in mind but compare actual figures.

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Now, as far as Torque and Horsepower go:
Torque is a function of Horsepower and Horsepower is a function of Torque. If you know one you can calculate the other as long as you know the RPM at which it was produced.

Here is the formula: HP = (TQ * RPM)/5252

Or flipped around: TQ = (HP * 5252)/RPM

So, a given HP at a given RPM will always result in a given TQ figure. If two engines have the same HP at the same RPM, they will by definition have the same TQ.

Therefore: RPM is King!!!! Not really, it's just that, mathematically, HP and TQ are simply different representations of the same thing (physics definitions are different however). What really matters is what you want to do with the vehicle. If you want to race you want your power at high RPM's, if you want to tow you'll need more HP at lower RPM's to make sure you can get to the higher RPM's.

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BertP,

Good point bringing the drive train into the equasion. I am guilty of oversimplifying the issue. Since most of us will simply use what the manufacturers supply and not change the entire drive train to make full use of the power plants potential I just take the drive train as a given and not a component that can be changed.

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The only point you made that I would disagree with is that if you had the right drive train the Hemi would outpull the Cummins on the hill. In theory what you say is entirely correct. In practice that would require a drivetrain that would keep the engine running at nearly 5,000 RPM's - that meets the very technical definition of "screamin". That drive train would require many, many gears and be provided at a very high cost and is not currently available to most people.

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Two thoughts that I think need to be considered:
(1) the Cummins produces it's maximum HP and TQ inside of it's normal operating range and the Hemi produces it's peaks outside of it's normal operating range. So given the reality of the drive train that you have to work with when you purchase a Hemi you will not be able to make full use of the power it has available.

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(2) the Cummins, with the drive train provided, has more torque after an upshift than it did before the shift. With the Hemi that is reversed. The Cummins will upshift at something between 2,000 and 2,500 RPM's depending on how hard you are accelerating. When it does the RPM's drop down towards it's peak torque RPM of 1600. The Hemi shifts at 2,500 to 3,000 RPM and the RPM's drop - it is never allowed to approach it's peaks near 5,000 RPM.

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To solve the problem the Hemi would have to have a drive train that allowed it to run up to 6,000 RPM's and then drop the RPM's down to 5,000 or so when it upshifted. That would allow it to return to it's peak power. You are correct that it is possible, it just doesn't pass the sniff test for being realistic.