On the contrary, there is an
On the contrary, there is an advantage to lower, peak power outputs, with relatively higher peak torque levels that diesels provide drivers. That advantages are called "efficiency", "fuel economy", "superior refinement" and "reduced engine wear" under heavy loads. I absolutely agree with what Thomas has asserted but it's missing an element or two. It is true that equally-modern and well-designed gas versus diesel engine will produce a gas engine with more all out performance, as in a better racer and more likely to accelerate up a hill even under a load, because, just as Thomas described with respect to the gas engine, the hp continues to rise with RPM along with torque. In other words, the rise in both performance measures more or less move together or linear all the way up to at least 4,000 RPM where the torque will start to peak, while the hp will continue to rise up to near redline.
Conversely, a comparable diesel will not have the same level of peak performance, because it's basically got all the toque right from the get go where the horsepower is very low, and then as the RPM rises above 2500 (the point at which the horsepower starts to really build), the torque starts to drop. So someone may ask what is the advantage to this? It's simple, when an engine is putting out a lot of power output (horsepower) it is using a lot of energy and using energy means that it's burning fuel, but a gas engine can't get torque at a low power output level, so when it's under a load or trying to maintain or accelerate up a hill, it's got to get to a higher RPM and build horsepower to get that torque. But a diesel doesn't need to drop gears or gain horsepower to get that torque; it's already got it. And therefore, if one is max towing up a hill in a diesel at or about 3000 RPM at just under peak torque; and another equally loaded vehicle with a gas engine is doing the same thing at 5200 RPM (even if there is a little power left in reserve to accelerate), the diesel driver is getting much better mpg, and the diesel driver is having a much improved, refined, driving experience than the gas-powered driver behind the wheel of a screaming engine.
Another aspect of this is usable power. Yes the gas engine has much more horsepower, but how often is the driver going to be driving in the RPM range to tap this power? If he or she is going to be at or above 4000 RPM often, then he or she is going to wish he or she was driving the diesel where he or she could do the same work with much less horsepower putting less wear on the engine, having a superior driving experience, and spending less at the fuel pump. If another driver doesn't need the horsepower very often, then he or she is going to wish for the diesel just because it get better mpg under lighter loads as well.
So, there are two valid arguments that those who prefer gas power will make: the cost argument, which is absolutely valid due to the EPA's fuel neutral policy, which makes an already-more-expensive-to-build diesel engine cost thousands more to market to the public; and then there is this all-out performance argument, which is also valid but only to those who want and prefer to drive vehicles that are "fast", as in racing fast, and do not care how much fuel they have to buy to go fast, even in high utility situations. It can be argued that diesels are slow versus race-inspired, gas engines; but "slow" is a relative term and most Americans are plenty satisfied with diesels from a performance standpoint, and most prefer them once they drive them due to the fact that diesel drivers can reach peak torque without dealing with a screaming engine.
So what this all comes down to for most Americans is the cost to drive the little Duramax versus the V6. If someone is in the market for a crew cab, with lots of bells and whistles, and most every active safety and towing option, then the Duramax makes sense, because then it's only $3730 more. But if all you wanted was a $25K extra cab truck, as you can get with the V6, and was hoping to spend no more than an extra $4K for a little Duramax; the you're out of luck, because GM won't let you have such a truck. You must pay at least $34K and take a highly-featured, towing version of the truck with lots of bells and whistles.
Then there are a few out there that want a truck that is ready for the racetrack. The Duramax is not for you either.