Clean Diesel: A New Era of Green Cars

Together with their superior durability and fuel economy, clean diesel technology enables diesel cars to rival gas-electric hybrids as green cars.

  • clean diesel green cars
    The universe of available green cars has expanded thanks to new clean diesel technology. Compared with a similar-sized gasoline engine, a diesel engine delivers about 30 percent better fuel economy, which also means roughly 30 percent less carbon dioxide emissions.
  • Helen and John Taylor
    Fuel-efficient driving team Helen and John Taylor drove a 2009 Volkswagen Jetta TDI 9,419 miles on only 12 fill-ups.
  • How clean diesel works
    Shown above is Audi’s clean diesel engine and ultra-low emissions system, which is a good example of how all clean diesel systems operate. Diesel exhaust is first treated by an oxidation catalyst to convert carbon monoxide and unburned hydrocarbons into carbon dioxide and water vapor. A particulate filter then traps and burns off polluting particulate matter. Some systems also use urea injection to create ammonia for a reaction (in the final catalyst) that removes nitrogen oxide. The final result is a car that meets strict emissions standards.
  • 2010 Volkswagen Golf TDI
    The 2010 Volkswagen Golf TDI hatchback, formerly the Rabbit, has room for five and is rated at 30 mpg in city driving and 42 mpg on the highway.
  • 2010 GMC Sierra 2500HD diesel
    The diesel version of the 2010 GMC Sierra 2500HD has a 40 percent higher maximum torque rating than the gasoline equivalent of the truck.

  • clean diesel green cars
  • Helen and John Taylor
  • How clean diesel works
  • 2010 Volkswagen Golf TDI
  • 2010 GMC Sierra 2500HD diesel

Whatever notions you have about diesel cars, forget them. Long gone are the days of smelly, black plumes of smoke, noisy engines, slow acceleration, and sometimes-finicky operation. The technology has evolved significantly in recent years. Diesel cars are now green cars and a strong green transportation option.

Modern diesel powertrains are quiet, clean, smooth, reliable, powerful, durable and economical. A diesel vehicle will usually cost more than a comparable gasoline vehicle, but the diesel engine’s more robust design means that, with proper maintenance, it should last considerably longer. Plus, some clean diesel cars qualify for a federal tax credit. (See our 2010 Clean Diesel Cars, Trucks and SUVs and 2012 Clean Diesel Cars, Trucks and SUVs charts for much more information on diesel vehicles.)

For generations, diesel power has been the best choice for work-intensive applications, with no other engine delivering as much stump-pulling power. What’s evolved is how the engine compresses and ignites the fuel to propel the vehicle — a change that has capitalized on diesel’s inherent advantages while virtually eliminating the traits that previously made diesel dirty.

Diesel enthusiasts now contend that a diesel car delivers fuel economy on par with that of a gasoline-electric hybrid, and also offers a better driving experience. (See Clean Diesel: More Efficient Than the Prius? to find out how clean diesel vehicles measure up with gasoline and hybrid vehicles in mpg, price, greenhouse gas emissions, annual fuel cost, and more.)

How Diesels Are Different

Aside from using diesel fuel rather than gasoline, diesel engines operate in a fundamentally different way than gasoline engines. A diesel engine doesn’t have a spark plug to ignite the fuel/air mixture in the engine. Instead, a diesel engine ignites its fuel via the heat created when the fuel/air mixture inside the cylinder is compressed sufficiently. These high-compression engines are controlled by the timing and duration of the fuel injection events rather than by the firing of spark plugs, as with gas engines.

It used to be that you could tell the difference between a gasoline engine and a diesel engine just by the sound. But the latest clean diesel cars — even those with four-cylinder engines — are quiet and smooth, with only a hint of the old telltale diesel clatter when they’re driven at certain speeds or under certain conditions. Luxury diesel models are nearly silent.

Mike Kiernan
1/30/2012 3:17:37 PM

Being up here in Northern Maine the really big question here is the diesel fuel freeze issue. I'd love to have a diesel, even one of the old M-35's, up here for both business and for the monthly grocery store run. Hey, when you're 35 miles from town in the snow for 6 months a throw, something has to give ! But every time I ask any truck dealer about the diesel fuel freeze problem and any ideas as how to solve it, all I get is a 1000 mile stare. Jeep was supposedly in the process of building the Jeep with a diesel and getting into the US market. So far, n-a-d-a !. Anyone have a fuel freeze solution, come up here and make money off it !!!!

3/5/2010 11:38:38 AM

Sorry for the double post, but it takes so long, it's hard to tell it went through. 4: Range issue? Seriously not much of an issue for most of us (not all of us as some commute way to far without the mass transit option) as we rarely, on a daily basis, drive further that an Electric would get us. An Electric vehicle or two for primary transportation, local trips and getting around town, and one diesel/Hybrid for the longer trips, or as a back up vehicle, would be huge on fuel savings for every family. BTW, my unmodified 1991 Ford F250 with the 7.3 "old tech" Diesel is capable of getting 18 city mpg and 24 highway mpg (at 50 to 55 mph). That is if I try real hard to use a light throttle and don't care that I'm seriously pissing off everyone behind me that is in a hurry and also shutting the engine down at long red lights! If driven normally to keep up with the other traffic and idling at red lights, it only gets 11 to 13 mpg city and 17 to 18 highway mpg (at 70 to 75 mph).

3/5/2010 11:02:52 AM

A few facts. 1: Emissions testing. Diesels emissions are tested at "per gallon" levels, but Gasoline emissions are "per mile", so better mileage makes it look cleaner. If Gasoline was tested at "per gallon" like diesels, the test and comparison would be fair, and diesels better efficiency would give it the edge. 2: Trucks idling. Yes, the whole "hotel load" aspect is there but they now have small generators that will supply that without the main engine idling. Also, diesel engines have a HUGE MASS and a HUGE COOLING SYSTEM,, and that takes a long time to warm up, and engines experience higher wear rates at less than operating temps, so they want to keep it warm. 3: Those in power want to continue to make money, and big oil is the power in the USA, so why would they want high mileage transportation? Proof? Ford, Chrysler, and GM way back in 1996 (THAT'S 14 YEARS AGO PEOPLE!) all had Diesel powered Hybrid cars ready for production. Other manufacturers were also were building them, but Toyota was the only one not to scrap their program and went to market with their Hybrid the next year in 1997, but only in Japan. WHY HAS NOBODY ASKED "WHY WAS THE PROGRAM SCRAPPED BACK IN 1996 IN THE USA?" Here is a link to an article from back in 1996.



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