Why do commercial vehicles use diesel engines instead of gasoline?
I know that diesel is generally cheaper than gas, and that diesel engines seem to last longer and are slightly more efficient, but is there any one or two overriding reasons from an engineering standpoint that large vehicles are usually designed to burn diesel instead of gas (I know that diesel stinks & tends to pollute more, so presumably that is why we don't see more diesel cars)?
Update:All good answers. I'll let the voters decide. Thanks for answering.
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WAY more efficient.
I don't know about big rigs, but look at motor homes for example:
A big Class A with a gas engine might get about 8 mpg
The same vehicle with a diesel might get 10 mpg.
While that doesn't seem like a lot, when you do the math, the diesel gets 25% better fuel mileage!!
As far as cars go. They have stricter emisssions requirements and manufacturers must limit the amount of polluting vehicles they produce.
Hope that helps.
I don't know about trucks, BUT my 1982 VWdiesel rabbit still gets 40 miles to the gallon. So I'm not too concerned about the cost differntial vs gas! Diesel is currently a few cents more expensive than the highest grade of gas, and I suppose it'll stay that way. But my car is still cheaper to operate than a new gas car. I do have an extra engine which I plan to rebuild to hopefully lessen my car's environmental debt. The original owner's manual explicitly says that no warmup period is required. You turn the key on, wait 15 seconds or so for the glow plugs to warm up, then engage the starter, take your foot off the clutch and go on your way. The manual explicitly says never to idle the engine.
Diesel is safer to handle, less flammable and easier to store.
It is also more efficient than gasoline. There are more calories to burn in diesel. It requires less refining.
The things that make diesel more polluting make it run better in diesel engines. Many of the impurities help lubricate the engine as it runs. Removing them makes it more expensive than gasoline. Diesel is a good product and a well developed technology.
Diesel engines don't burn the fuel efficiently when the engine is too cold. This is true for gasoline engines as well but to a lesser extent. So if you use your car only for going to the mall, you're better off with a gasoline engine.
Diesel engines are substantially more efficient than Otto engines [conventional gasoline] There have been problems with reliability of Diesels for automotive use -- strict attention to oil is required because of the high pressures involved. Diesels have become increasingly popular, especially in Europe, as petroleum prices have risen, and are almost universally used for large trucks whose fuel consumption is a major factor in total operating costs. I had a Diesel powered automobile, and was very pleased with it -- it got 44 mpg.
Check out the VW Golf. Comare the TDI diesel to the gasoline model. The highway mileage is 44% better for the diesel. That is HUGE!
Because the engines last longer than conventional gasoline engines and they are more powerful and it used to be that diesel fuel was less expensive then gasoline, however that has changed to the opposite most of the time.
Diesel engines have better torque than speed.
Torque is the ability to rotate with higher weights.
Diesel engines produce more torque at lower speeds than gasoline engines do. This is very important for towing. They also get better milage.
I think it is cheaper for them cuz they use alot of gas.
We should use electric cars really or cars that run on cornoil or water.