Will ‘Dieselgate’ turn into ‘Petrolgate’?

Posted on November 15th, 2016 by Rob Marshall

Diesel emissions

If you drive a diesel vehicle, especially in the city, the government will be out to get you. Or so we are to believe. With urban air pollution being a political hot-potato, not helped by the diesel emissions ‘cheating’ scandal (of which both carmakers and governments are to blame) I have become increasingly concerned by the ‘diesel-bashing’ that is gaining ground, because I sense that the complex issue of improving real-world urban air quality, in particular, is more complex than blaming just one type of engine.

Yet, I agree with the recent High Court Ruling that HM Government is guilty of breaking air quality laws. In my experience, the authorities have done nothing to clamp-down on illegal car modifying activities that increase diesel engine exhaust pollutants, such as garages removing anti-pollution systems (including diesel particulate filters and exhaust gas recirculation valves), and aftermarket ECU chip tuners and tuning box sellers/fitters, all of which are rife across the UK and prejudice real-world tailpipe emissions. While not promoted widely, if an engine is tuned to use less fuel and its emissions are unregulated during the exercise, CO2 emissions are likely to decrease but the remaining cocktail of gases are likely to be more toxic than the manufacturer intended. I shall not go into the ramifications about why all of this is illegal.

The problem with emissions (as with engineering in general) is that compromises have to be made and nothing is black-and-white. While petrol engines produce fewer quantities of certain pollutants in the real-world than diesels, the opposite is also true. Diesel engines produce very little carbon monoxide and hydrocarbons, for example. While politicians can employ simplistic sound-bytes, such as calling for diesel cars to be scrapped and replaced by new petrol (and petrol hybrid) alternatives, the result might see a welcome reduction in NOx emissions but this needs to be balanced carefully against the resultant real-world carbon dioxide emissions hike, as well as a careful analysis to see if levels of other toxic pollutants will increase, which may not have been considered in the aim of decimating the diesel car park.

Problem petrols

The ‘Dieselgate’ scandal promoted a trend of downsizing, mainly towards smaller petrol engines, including three cylinder units. They compensate for their diminutive cubic capacities by being turbocharged and tuned to produce outputs comparable with those of larger engines. While they have performed well in the (deeply-flawed) EU laboratory emissions tests, they are not as saintly in real-world conditions. Thomas Weber, head of R&D at Mercedes-Benz, has been reported as stating that the disadvantages of downsizing have been long-known by the motor industry. What else is the industry not admitting, I wonder?

While carmakers, regulators and green groups have been accused of knowing that real-world pollution levels were higher in real life, the advent of revised EU new car emissions testing has seen some manufacturers performing an impressive volte-face.

Speaking at the Paris Motor Show, the head of powertrain at Renault-Nissan admitted that the strategy of reducing engine capacities will allow the company no longer to meet emissions standards and that it has reached the limits of downsizing its engines. Perhaps we should expect to see larger and less efficient engines arriving in the future but, to me at least, this seems to be a perverse interpretation of progress.

Regardless, UK (and EU) regulators need to be more proactive in realising real-world pollution issues that affect direct-injection petrol engines, especially hybrids, such as their tendency to produce cancer-causing particulates, a factor that tends to be blamed solely on diesels. It is a little-known fact that the EURO 6 pollution limits for new car particulate emissions are the same for both petrol and diesel. Interestingly, no current new petrol cars are equipped with particulate filters but they are mandatory for diesels.

Hybrid hyperbole

As the majority of Hybrid cars are fitted with direct-injection petrol engines and many of them operate as taxis in built-up areas, they also should be scrutinised more heavily. Amazingly, hybrid cars are exempt from MoT exhaust emissions checks and so we cannot be certain that existing examples in everyday use are not pumping out excessive toxic emissions, when their engines are running. A further issue is that catalytic converters are only effective when kept hot, usually by a running engine, which casts a further doubt on the real-world eco-prowess of the hybrid that uses its engine only when it needs to. This is because engines are at their least efficient and most polluting, when cold and petrol engines take longer to warm-up and reach their optimum efficiency than diesels, which increases emissions disproportionately. Last October, I queried Mitsubishi, maker of the UK’s most popular Plug-In hybrid model, about what steps had been taken to ensure the effective treatment of tailpipe toxins from its part-time running engine. I am still awaiting an answer, despite following-up the query several times.

What are we to do?

The challenges presented by the rate of urbanisation (which refuses to slow – the ONS reported earlier this year that London’s population will grow to almost 10 million people within the next decade) makes reducing air pollution both more pertinent and challenging. However, just as in the medical profession, it seems that today’s recommendations tend to be discredited shortly afterwards, with the benefit of hindsight. I hope that politicians are not setting this up to happen again. By focusing on demonising diesel engines in favour of petrol and petrol hybrid alone, I worry that other issues are at risk of being ignored, which may rise and bite us in the future.