Diesel vs gas......................

I'll add the following with a qualification first - I'm a degreed mechanical engineer. This topic is the stuff I studied in school and it's what a lot of BSME's do for a day job.

What makes you think qualifications count? (Just funnin' ya. I'm a powertrain engineer and most people don't listen to me either).

Just to refresh your memory and put to bed some minor details;

Torque is a force. Like any force, it can be present without actually accomplishing anything. I can push on the side of a building with my hand and still apply a force without moving anything.

A force that moves something over a distance creates work. Work done in a certain amount of time is power.

Power and torque are mathematically related. Hp = torque x rpm/5252 in non-metric units.

The significant difference is that power is consistent throughout the engine/drivetrain system. Torque changes with gearing.

A moving vehicle requires a certain amount of power to move it at a certain speed (distance per unit time). It's a relatively simple formula that starts low at slow speeds when you're only overcoming rolling resistance and increases rapidly over about 30-40 mph as wind resistance builds. Any grades will tend to increase those requirements pretty substantially.

Gearing also forces the engine to operate at a particular rpm for a specific speed. Given some corrections for drivetrain efficiency, if the engine can deliver the required power at the given speed, you'll continue at that speed. Acceleration is actually a function of how much more power is available than is needed.

But remember, torque and power and mathematically joined at the hip. All these calculations can be done using engine torque, but the math ends up being more of a PITA. If you actually sit down with engine and drivetrain system data, you'll realize that anytime someone talks about great performance due to torque or power, similar math will get you to the same realization with the other.

Torque's real significance is at the only place where power doesn't exist (at the wheels anyway) which is when the vehicle is not in motion. Torque is significant in getting the wheels rolling or "startability" as it's called.

The efficiency and durability advantage of diesel doesn't tell the entire reason for thier popularity in commercial trucks. The fact is that diesels have yet to play by the same emissions rules as gas. That fact will potentially shake the heavy duty industry in the next decade as "fuel neutral" emission rules and low sulfur diesel fuel rattle the commonly held assumptions of diesel towing superiority.

Diesels really gained a heavy duty advantage over gas with the advent of turbochargers, allowing them to get substanial power to go along with low end torque (a byproduct of extra rotating masses and lower rated rpms). They were no longer "all grunt and no go" and commercial trucks could get fuel efficiency and speed making them economically superior.

2002 brought substantial emission reduction requirements met mostly with EGR and CAT's Miller Cycle operation. Fuel economy and price have taken a non-negligible hit and system durability has been affected somewhat.

2007 will virtually eliminate smoke emissions and will introduce aftertreatment systems for the first time, again impacting cost, economy, and system durability negatively.

2010 will virtually eliminate NOx, again with predictible results.

And all of that doesn't take into account the shift in fuel prices that can occur if diesel cars become as popular as they are in Europe once the emissions get cleaned up. I mean, just look at how much howling goes on when the heating oil season kicks in.

This is not to say that diesels will disappear, but it will even the field for gasoline which will continue to improve. I've seen knowledgable industry predicitions that diesel will lose its effective economic advantage by the middle of the next decade. Do I agree with the predictions? I do heavy diesels and I don't think things are that dire, but the preposterous notion that either cycle has a God-given superiority would prove to be economically fatal.

Yep. Right now diesels give better fuel efficiency that can offset the extra cost with solid performance. But I can buy gas at no less than 3 stations within 4 blocks of my house. I haven't found an in-town diesel station yet. And my wife doesn't like diesel. And I don't tow that much that I going to recognize much savings, if any, long term.

At the end of the day, buy what you like and what suits your job. It's not a simple one dimensional question and simple platitudes serve no purpose.