BMW denies emissions tampering but watchdog says diesel engines have ‘peculiar behaviour’

ICCT claims BMW 520d performs strangely on emissions tests, as anti-trust scandal whirls

BMW issued strong denials of colluding with other car makers over the costs of diesel emissions systems over the weekend, as EU officials raided the company's Munich headquarters. The raid was not specifically about tampering with emissions results, or adding 'defeat devices' as did Volkswagen, and BMW has been quick to point that very fact out.

“The BMW Group wishes to make clear the distinction between potential violations of antitrust law on the one hand and illegal manipulation of exhaust gas treatment on the other,” said an official Munich statement. “The BMW Group has not been accused of the latter.”

However, the International Council on Clean Transport (ICCT), a part of the research group that first uncovered the VW scandal two years ago, has released a report that points an accusatory finger at BMW over the performance of its big-selling 520d diesel executive saloon.

According to the ICCT, the BMW 520d performs well on the specifics of the new Real-world Driving Experience (RDE) test, but shows huge variances in emissions performance outside of those parameters.


ICCT tested a BMW 520d, a Nissan Pulsar 1.5 dCi, an Opel Insignia 2.0 CDTI, and a petrol-engined VW Polo. All cars passed their NEDC emissions tests easily. When ICCT applied the ARTEMIS test (a test that is based on a large database of European driving patterns and is closer to real-world driving style than the NEDC) all vehicles saw increased emissions of dangerous Nitrogen Oxide (NOx). The Nissan performed worst here, at almost 66 per cent worse than the official NOx limit, while the BMW and Opel were also above the limit, by close to 20 per cent respectively. Only the petrol Volkswagen performed adequately - 0.7 times the official limit.

When the ICCT conducted a test equivalent to the new RDE test, and then a testy designed to be even tougher and more ‘real world’ than the RDE itself, things became very interesting. The BMW’s NOx emissions in particular surged, as did the Opel’s, while the Nissan and Volkswagen exhibited roughly the same overshoot of the regulations as they had in the lab tests.

According to the ICCT’s report “in contrast to the Volkswagen Polo gasoline car, which produced results on the road that were consistent with the laboratory test, all three diesel vehicles emitted NOX at levels well above the future RDE conformity factor of 2.1 times the Euro standard: 5 times for the BMW 520d, ten times for the Opel Insignia, and 16 times for the Nissan Pulsar.

Manufacturers will design RDE-compliant versions of these diesel vehicles. But will that be sufficient to cover most of the emissions encountered in real-world situations? For the second series of on-road tests, we looked beyond the RDE requirements and drove the vehicles more dynamically than the RDE test specification permits, but under conditions that do occur in real-life situations. This revealed another part of the story. That all tested vehicles were sensitive to a “sportier” driving style.”

BMW has been singled out for criticism in this test because, says the ICCT, it had the most unusual results. “The BMW 520d demonstrated peculiar behaviour by scoring the best, relative to other diesel vehicles, under RDE-compliant conditions, and simultaneously the worst-with 40 times the Euro 6 limit-under non-RDE-compliant driving conditions. Why such a difference? One could argue simply that a more dynamic driving style requires more fuel, leading to the emission of more pollutants” says the report.

But when ICCT examined the results more closely it became clear that the 520d had out-performed the other two diesel models during the limited RDE testing simulation, but then suddenly started emitting much more when driven in a manner more alike to real driving conditions. “A deeper investigation also revealed a measurable discrepancy in the behaviour of the lean NOx trap aftertreatment system in the BMW 520d, whose NOx purges were never triggered under more dynamic conditions. It is as if the vehicle had no NOx aftertreatment, similar to a Euro 5 generation vehicle at best.”

BMW has previously strenously denied any accusations os diesel wrongdoing, saying in a statement that “the BMW Group categorically rejects accusations that Euro 6 diesel vehicles sold by the company do not provide adequate exhaust gas treatment due to AdBlue tanks that are too small. Technology employed by the BMW Group is clearly differentiated from other systems in the market. We compete to provide the best exhaust treatment systems: unlike other manufacturers, BMW Group diesel vehicles employ a combination of various components to treat exhaust emissions. Vehicles which use urea injection with AdBlue (SCR) to treat exhaust emissions also employ a NOx-storage catalytic converter. With this combination of technologies, we fulfil all legal emissions requirements and also achieve a very good real-life emissions performance. This means there is no need to recall or upgrade the software of BMW Group Euro 6 diesel passenger cars.

“In addition, the combination of both systems, together with exhaust-gas recirculation, requires a lower level of AdBlue injection and leads to a very low AdBlue consumption in comparison to other manufacturers. This enables an optimised tank size while also achieving very low emissions in real-driving conditions. Furthermore, BMW Group diesel vehicles have a simple refill solution through the tank lid or engine hood, depending on the model. BMW Group customers are informed by the vehicle in good time and repeatedly concerning a low AdBlue fill level. If this is ignored, the vehicle eventually prevents operation.”

The ICCT, though, thinks that this might just be the tip of a new emissions iceberg (presumably one that’s melting pretty fast…). It is concerned that, once again, car makers are seeing the testing regulations as things to be met in the word, not the spirit, and that they will simply find ways of bypassing any new test in order to save money or make life apparently less stressful for their customers. “The upcoming RDE on-road test procedure is an important step toward lowering real-world emissions, but it will not bring down NOx emissions from diesel passenger cars in all circumstances. At this critical moment, manufacturers have an opportunity to win back customers’ trust in diesel technology, by showing that NOx emissions can be consistently low, even outside the prescribed rules” said the ICCT. “Our analysis shows that, in this regard, gasoline technology is clearly a step ahead of diesel technology; for diesel, there are few incentives for manufacturers to control NOx emissions outside of the current testing conditions. The success of the RDE regulation will depend on the will of manufacturers to prove that they have learned a lesson from Dieselgate by beginning to focus on reducing real-world emissions, not just on passing a particular test.”

These tests come at a time when car makers could be forced to reveal exactly what it is they are doing to control their vehicles' emissions. Environmental advocacy group Client Earth has launched a legal challenge which could see car makers forced to reveal the precise workings of their emissions control systems and technology. The action has actually been taken against the European Commission, in an attempt to force it to use a section of its regulations that says car manufacturers must explain what effect any variation to the emission control system has on emissions to type approval authorities, the officials who clear a car as fit for sale.

Client Earth is concerned that this regulation, which came into force last month, has no provision for transparency, and that car makers can continue hiding what they do behind a veil of secrecy, citing commercial and competitiveness pressures.

ClientEarth chief executive James Thornton said: "The Dieselgate scandal showed us we couldn't rely on these national approval authorities to protect the public and how damaging secretive behaviour by car manufacturers over emissions can be. The illegal levels of air pollution in towns and cities across this country are down in large part to diesel vehicles. A cosy stitch-up between manufacturers and the authorities will do nothing to reassure the public that the industry has learned its lesson after Diesel-gate.

“Air pollution has been linked to heart and lung disease and can trigger heart and asthma attacks. With people’s health at stake, we cannot allow the car industry to hide behind this smokescreen, we must have transparency.”

Neil Briscoe

Neil Briscoe

Neil Briscoe, a contributor to The Irish Times, specialises in motoring