Diesel engines have been the fuel of choice for many years in the UK. However, recent controversy around diesel emissions and the pollution they generate, particularly in urban environments, has led to some misleading and confusing headlines. So what are the facts?
A few years ago, diesels were being heralded as superior alternatives to petrol vehicles, offering new technology that reduced emissions and vastly improved economy to boot.
Reducing CO 2 emissions has been a serious priority for the makers of diesel cars because of this. That’s why, typically, a diesel engine emits 20% less CO 2 than an equivalent petrol engine.
A rise in the awareness of the harm caused by another emission, nitrogen oxide (NOx) has more recently caused concern. European emission standards require Diesels to produce below 0.08g/km of nitrogen dioxide which is, an 86% reduction verses standards at the beginning of the decade, although this, is still 33% higher than equivalent new Petrol cars requirement. Concerns are also being raised around actual emissions in Urban and real world driving situations.
But, not all modern diesel engines work or perform the same way.
Are manufacturers doing anything to combat NOx emissions?
YES! Diesel emissions have been in the spotlight since 1992, when European standards were introduced to gradually reduce their harmful effects. The current standard, known as Euro6 was introduced in September 2015, and reduced acceptable NOx emissions to just 0.08g/km.
Conscientious manufacturers like Mazda have been working on emissions compliance for a long time, and in fact, our SKYACTIV-D engines complied with Euro6 emissions restrictions as early as 2013, two years before the standard was even introduced.
This is reflected and recognised by government policy. When the London Ultra Low Emission Zone is introduced in 2019, Euro6 compliant vehicles will be able to enter the zone free of charge.
Whereas some manufacturers have introduced engines that combine a ‘NOx trap’ and technology that adds a liquid treatment (called AdBlue) to convert NOx into nitrogen and water, Mazda diesel engines currently (correct as at 2017) do not, as our latest SYYACTIV-D engines are naturally super-efficient, just as they are.
Okay, so what makes SKYACTIV-D engines so great?
Mazda’s SKYACTIV-D technology reduces the fuel compression ratio much lower than traditional diesel engines. In fact, at 14:1, it’s the lowest in the world. Put simply, that means that the temperature and pressure at which the fuel will optimally work is also much lower.
For the price of a longer ignition time of just half a millisecond, the air and fuel gets longer to mix together properly, resulting in much more uniform and efficient combustion. And that means the CO 2 and NOx emissions are also reduced as part of the process.
So, diesel is still a good choice then?
If you regularly drive long distances or tow, diesel is still going to be your most efficient and economical choice. According to the SMMT (Society of Motor Manufacturers and Traders), diesel drivers on average cover 60% more miles than those opting for petrol, so those lower fuel bills will make a difference. And the naturally higher torque a diesel engine delivers makes them great for towing or carrying heavier loads.
So, while traditional diesels do produce more harmful polluting emissions, and some manufacturers have had to integrate costly and time-consuming technology to counter their effects, Mazda’s SKYACTIV-D engines pass the strictest of standards (Euro6) with ease. If your lifestyle demands a diesel, you can be assured that our engines have been developed to exceed current emission standards, including CO 2 and NOx.