Currently reading: Mercedes rejects real-world NOx criticism
Mercedes clarifies its stance in the wake of new Dutch environment agency emissions findings

Real-world tests have recorded the Mercedes Mercedes-Benz C-Class C220 TDi BlueTec emitting 40 times more NOx than the legal limit in laboratory tests. However, Mercedes says the results are a consequence of real-world tests not reflecting official procedures, primarily because of the low ambient temperature during the test.

The tests were conducted by Holland’s Organisation for Applied Science Research (TNO) on behalf of the Dutch Minister of the Environment.

Mercedes says the discrepancy is partly down to the exhaust gas recirculation (EGR) process operating differently between five and seven degrees centigrade, a process it says is aimed at protecting the EGR cooler. Official laboratory tests that define whether a car is legal are conducted at 22 degrees centigrade.

Mercedes says this practice is fully legal, and that it is required to ensure the regulated requirement of delivering full functionality of the exhaust gas after-treatment system up to at least 160,000 kilometres. However, critics, while accepting the legality of the system, have suggested that such a device should be banned as it means the cars are hugely more polluting in low temperatures.

A Mercedes statement read: “Daimler AG once again absolutely rejects the inherent accusation of manipulation. Mercedes-Benz vehicles fully comply with the national regulations in force at the time of vehicle registration.

“We absolutely reject speculation or interpretation that possible deviations between test-bench measurements and measurements made during real driving conditions can only be explained by manipulation. No defeat device, ie a function that improperly restricts the effectiveness of exhaust-gas after-treatment, is used by Mercedes-Benz. Neither do Mercedes-Benz vehicles have a function that automatically recognises when a vehicle is being tested.”

However, as a consequence of the claims, a pressure group in Germany, Deutsche Umwelt Hilfe, has called on Germany’s automotive regulator Kraftfahrt-Bundesamt (KBA) to withdraw the EU-wide type approval for all diesel-powered C-Class models, or have the cars banned from all inner cities when temperatures drop below 10 degrees centigrade.

If type approval were withdrawn, affected cars would have to be taken off sale.

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bomb 5 February 2016

Makes you wonder how many

Makes you wonder how many more thousands of tonnes of crap is being ejected into the air each year, over and above 'official' figures. And that's before you take into account the aging diesel vehicles.

I've developed a real nose for stinking cars and vans that aren't that old when I'm out walking the dog (not difficult). The 5-15 year old stuff are particularly bad, the high pressure injection pumps were good for torque but not soot and acrid smells.

405line 5 February 2016

Unacceptable excuse

"Mercedes says the results are a consequence of real-world tests not reflecting official procedures" couldn't stuff make this up, so knowing this they still did's not a good situation. Magazines now need to pool together and publish generic independant emission results. What are the goverment doing eh? I tell you what they are doing, what they are doing for example is failing cars because the indicator lightbulb is showing too much white....meanwhile back in the real world.
spqr 5 February 2016

Re: Petrol CO emissions

Campervan is correct to say that petrol engines produce more CO than diesels but once the catalyst has warmed the CO emissions are much lower having said that petrol cars with catalysts still produce more CO than diesel cars, although exhaust emissions of NOx and particulates are much lower than diesel cars. In fact particulate emissions from petrol cars are so low that they are not routinely measured. What Campervan failed to say is that diesel engines still emit far more NOx and particulates that petrol engines even when the DPF has started to operate. But the DPF will not reach an operating temperature for up to 50 miles which most privately owned diesel cars never do being used much as a petrol car would be for short journeys. This is why a particular BMW dealership I know replaces between 20 and 50 prematurely failed DPFs per week. On a cold day a petrol car may take up to 10km to warm up and operate at maximum efficiency; a diesel car may only take 5km and overall, diesel cars emit less hydrocarbons, carbon monoxide and lead pollution than petrol cars, but produce more NOx, noxious gases and significantly more particulates. It is the NOx and particulates which cause smog, respiratory diseases, heart disease and cancer according to the World Health Organisation. According to Air Pollution website "particulates may be seen as the more critical of all pollutants, and some estimates have suggested that particulates are responsible for up to 10,000 premature deaths in the UK each year". So when xxxx says ban diesel now he has a point.