Today, if you're a car company and you offer a diesel engine in this market, you have to go to great lengths to show consumers that it's less harmful to the environment than a gas-powered engine. That's why marketing types have come up with TDI Clean Diesel and EcoDiesel and BlueTec and so on, rather than just plain old "diesel." How much cleaner are today's oil burners, though?

Well, according to a study from the UK's Society of Motor Manufacturers and Traders, these torquey engines are cleaner than they've ever been. Diesel engines sold in Great Britain churn out 21 percent fewer pollutants than diesels sold in 2003. At the same time, fuel efficiency is up 27 percent compared to ten years ago.

Overall, the average diesel in the UK pumps out just 128.3 grams of carbon dioxide per kilometer, which is down nearly 30 percent since 2000, according to SMMT. It also marks the first time average diesel emissions have dipped below 130 g/CO2 per kilometer. To put that level of cleanliness into perspective, a gas-powered compact crossover like the Ford Kuga – our Ford Escape – produces 179 g/CO2 when fitted with a 1.6-liter EcoBoost four-cylinder.

"Motorists today benefit from much cleaner diesel cars than those that were on the market even ten years ago," Peter Fouquet, President of Bosch UK told HybridCars.com. "As diesel car sales continue to rise, we are focused on constantly innovating new technologies that help reduce emissions from diesel cars and make them cheaper to run."


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  • 75 Comments
      Matt
      • 9 Months Ago
      The bigger issue is that all diesels have particulate filters, but in the US, no gas car does. Direct injected gas engines produce tons more cancer-causing particulate emissions than diesels. Until the government forces automakers to install particulate filters in DI gas cars, diesel will continue to be the better option if you are concerned about human health.
        in2dwww
        • 9 Months Ago
        @Matt
        Why are there so many negative votes on this post? It's an actual fact and it shows how everyone's lack of knowledge on the subject supports the government's ideals that cheaper solutions are the only (and best) solution. Factually, all direct-injection engines run richer. This means that it's necessary to develop advanced methods to go along with the innovative changes. Down voting these factual comment shows just how half-baked the logic is for direct-injection gasoline engines.
        thomas.leopard
        • 9 Months Ago
        @Matt
        This is true, autoblog actually had an article about DI engines emitting less CO2 but more toxins. I dont get why so many downvotes.
        icemilkcoffee
        • 9 Months Ago
        @Matt
        Agreed. The regulators haven't kept pace with the technology here.
        Lachmund
        • 9 Months Ago
        @Matt
        people in denial voting you down? i see
      FuelToTheFire
      • 9 Months Ago
      Why can't I rate comments anymore?
      Koenigsegg
      • 9 Months Ago
      then why is europes air so bad. All they drive is diesel cars. There is nothing clean about diesel. This **** really has to stop and its so simple. humans are so slow.
        Lachmund
        • 9 Months Ago
        @Koenigsegg
        european air is bad? do you actually even think before you post stuff on this site?
          ctsmith1066
          • 9 Months Ago
          @Lachmund
          I think he was referencing the recent bad air quality in Paris, which has been all over the news.
          Gabbo
          • 9 Months Ago
          @Lachmund
          Do you like to breath soot, Lachmund ? It's not so good for you .....
      brotherkenny4
      • 9 Months Ago
      Or you could say that they still produce the majority of pollution they always did. Or, you could say they produce nearly as much pollutions as old lowtech varieties from the acient past. Or, you could say there has been virtually no improvement in deisel with regards to the amount of pollution they produce. Just because you attempt to capture and control the words, not everyone buys it. Long live big brother and may the Ford be with you.
      lad
      • 9 Months Ago
      Diesel is not a good fuel for use in an internal combustion engine. The fuel is expensive because of the preconditioning necessary to remove the contaminants such as sulfur. And, diesel engines are more expensive because of the components they use, i.e. high pressure pumps for direct injection and expensive and complicated emissions systems, especially the exhaust system. In fact in some cars an additional tank of urea liquid is needed to supply nitrogen of exhaust cleanup. The torque curve of the engine shows a very narrow peak unless it has a turbo assist, which makes it even more expensive. The advantage of a diesel is the fuel has more potential energy than other fuels...that's it! Remember how diesels lasted for two hundred thousand miles? Well, they don't do any better than gas engines now that the sulfur has been removed. Don't see a reason to buy one except to create a market for the greedy oil companies.
        Joeviocoe
        • 9 Months Ago
        @lad
        Wrong... the mpg gains far exceed the 'extra energy content' of the fuel. That is because of the compression ignition cycle allows for leaner ratios than strictly stoichiometric. That is why GDI can achieve great gains too. And you are wrong about the sulfur too. I've got 300,000 miles on my engine, most of which on ULSD.
          Jerry
          • 9 Months Ago
          @Joeviocoe
          Thank you
          Joeviocoe
          • 9 Months Ago
          @Joeviocoe
          Well, I am glad automakers are working on better gasoline engines (to behave a bit more like the diesel cycle). But it seems like they are asymptotically reaching a limit of diminishing returns here. Non-hybrids and newer non-diesels still cannot crack the 40 mpg (combined MPG) mark. They all get their 40+ hwy mpg by designing to the highway test (taller gears)... and many of them are dealing with more and more customer lawsuits about not having real world fuel economy. It seems electrification and "plug-ins" are the only way beyond these fuel economy and emission limits, while still maintaining performance, safety and comfort.
          AcidTonic
          • 9 Months Ago
          @Joeviocoe
          Don't forget it has less pumping losses too due to lacking a throttle blade. The engine is always at full throttle on the air intake.... the fuel quantity is what changes when you move the throttle. Where as a gas engine mechanically fights the engine to breathe air creating pumping losses. You cannot use fuel to throttle a gas engine because when it leans out as you cut the fuel detonation happens. Diesel fuel doesn't detonate at lean ratios so it works out. If only we could get a gas engine stable enough under fuel controlled throttle to remove the throttle plate. Should offer huge economy improvments if someone could build one.
          Rotation
          • 9 Months Ago
          @Joeviocoe
          AcidTonic: Diesel fuel detonates at ALL ratios. That's what Diesels do. We can't make gas engines work just by putting in less fuel because at low ratios the fuel burns too fast (detonates) and makes too much NOx. Even if you delay putting in the fuel (it can't detonate until it is in the chamber, right?) it still creates too much NOx. Diesels fight this problem too, their production of NOx is one of the problems Diesels have to overcome. More advanced EGR is being used to try to fight this on both gas and Diesel engines. If that can be made to work, then we can get lean burn on gas engines and then we can use compression ignition on gas. GM, VW and many Japanese companies have said they are working on this. None has made it work yet.
      jebibudala
      • 9 Months Ago
      Only if the EPA can get cows to pollute 20% less with their methane pollution. Stupid cows. We should eat all of them.
        Goahead
        • 9 Months Ago
        @jebibudala
        How about eating much LESS of them? Law of simple economics: Supply & demand. You eat less meat, healthier body, less cows produced due to less demand, greener planet. It's one of the best win win situation in history!
      in2dwww
      • 9 Months Ago
      Go find yourself a nice, used, 100k+ mile TDI car at your local used car dealer. 2009 on up. Then have a look at the tail pipe. You won't see a spec of carbon or black soot inside the tail pipe. I know this because I was an idiot and sold my MKV VW Jetta TDI 6-speed manual at 115k miles. Then go look at any new car with direct injection gasoline power. Take a nice look at the soot drooling out the tailpipe after just 800 miles. Then go online and check out the plethora of information on carbon build-up on intake valves (ahem.. Mini, Audi, BMW, etc). Diesels are the better option for people who drive highway miles. I won't knock a gas engine, but when it comes to clean exhaust, the diesels win. You may cite higher NoX emissions, but the diesel actually emits lower carbon emissions than a hybrid. Don't knock a diesel until you try one.
        Rotation
        • 9 Months Ago
        @in2dwww
        Diesels do not produce lower carbon emissions than a hybrid. Not for equivalent power output.
      Corey Blue
      • 9 Months Ago
      One who cares. Two this article is incorrect, tier 4 final compliant diesels actually clean the air relative to the pollutants they take in. This article is a shame.
        Jerry
        • 9 Months Ago
        @Corey Blue
        Is that sarcasm or are you actually serious?
        Joeviocoe
        • 9 Months Ago
        @Corey Blue
        Particulates can be cleaned out yes... the majority of pollutants and GHGs... no.
      Corey Simmons
      • 9 Months Ago
      I work a refinery and it takes a lot less refining to make diesel. Gasoline had to go through a hyrdotreater to remove sulfur then through a reformer to crank up the octane. Once that is done, it goes through a Benzene saturation unit to remove a lot of benzene so you don't breath it at the pump. Then add ethanol that is required in states like California, and cleaning detergents for fuel injection systems. Diesel comes from the same distillation tower as gasoline, but only has to go through a Hydrotreater to remove sulfur. To make ULSD, we only have to run a little higher temp in the reactor to make 5 to 10ppm sulfur. No need to add anything else, other than some jet for quantity. Diesel in states like California usually cost more because of taxes.
        b.rn
        • 9 Months Ago
        @Corey Simmons
        Diesel costs more in most states because of supply and demand. You can't make as much diesel from a barrel of oil (even with fracking), low supply. Europe subsidies diesel to the point that they wind up importing a lot of it form the US, high demand.
          Corey Simmons
          • 9 Months Ago
          @b.rn
          That is true, but we could also produce more diesel in our hydrocracking units. Gasoline is more profitable with a higher demand. Many times we ship diesel to South America or Europe where people drive a lot more diesel vehicles.
      Myself
      • 9 Months Ago
      But that's only CO2 - add nitrious oxides to the equation and you find diesels more polluting than gas engines. Japanese pollution norms do - and in Japan, the only diesel that can be considered clean is Mazda's SkyActive.
        Matt
        • 9 Months Ago
        @Myself
        DI gas engines produce over 10x more particulate emissions than diesels, since all diesels have a DPF, and no gas cars currently use a particulate filter. Particulates might be the "worst" emission of them all in terms of health and environmental impact.
          in2dwww
          • 9 Months Ago
          @Matt
          I just love the crack-pot negative votes on this factual rebuttal comment. It shows the lack of education and exposes the mere fundamentalism of supporters for an alternative gasoline method (hybrid) that has no merit.
        atc98092
        • 9 Months Ago
        @Myself
        If you mean untreated diesel exhaust, then yes NOx is higher. But since every diesel sold in the US has exhaust treatment, the NOx levels are about the same as most (but not all) gas engines. And many of the other emissions are even lower than a gas engine.
          montoym
          • 8 Months Ago
          @atc98092
          Agreed. Diesels have to pass the very same emissions standards as gasoline engines these days (at least in the US). They do not pollute more, if they did, they wouldn't pass the emissions standards.
      ground
      • 9 Months Ago
      Ironically without the DPF and urea injection they would get about 20% better fuel economy... so is it really greener?
        in2dwww
        • 9 Months Ago
        @ground
        The 2008 Mercedes E320 BlueTec does not use AdBlue (urea injection) but it does have a DPF. The 2012 Mercedes E350 BueTec is the same engine, but uses AdBlue. The difference in economy between the two is greater than 20%, and it's the W212 E-class that performs better even with the AdBlue. In terms of being green, the more efficient W212 and the fewer NoX from the exhaust of the W212 would suggest that it's greener. This is at least limited to the advancement over time for the same engine and different body style, but it's relevant to advancement in the United States.
        Jerry
        • 9 Months Ago
        @ground
        Maybe in the automotive world, but tier4 industrial engines are up to 15% more fuel efficient across all brands. You can really clock forward that fuel pump and smoke like hell when you have a DPF to catch everything. I am willing to bet that the tier automotive engines are also more efficient, but the reduced fuel economy is a result of the added weight for the after treatment systems.
        Ryan
        • 9 Months Ago
        @ground
        Agree ground. I've driven the 2014 Euro diesel Grand Cherokee and the US version. Euro gets about 10-15% better fuel economy, doesn't use urea/DEF/adblue, but has slightly worse tailpipe emissions (still far better than the gas alternative grand cherokees though)
      2 wheeled menace
      • 9 Months Ago
      What about gasoline cars, by comparison?
        paulwesterberg
        • 9 Months Ago
        @2 wheeled menace
        Fallacies of Omission http://www.emdashprof.com/373/tomatoes/omission.html
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