Editor's choice
13 Jan 20

WLTP and 95g will save the diesel engine

The new European type approval method has caused an increase in CO2 emissions – even when converted back to their NEDC equivalent. At the same time, Europeans have massively switched to petrol cars. Arguably, OEMs need diesel more than ever. In fact, so do many corporates.

WLTP, the new type approval method for fuel efficiency and emissions, has caused an increase in the average CO2 emissions of a carmaker, even if they are still back-translated to a virtual NEDC value. The numbers vary between +5 and +15% (from NEDC1 to NEDC2), depending on the source.

That’s one thing. Another is that more consumers are turning to petrol cars in general and to crossovers in particular. According to the EU, the average fleet emissions went up to 120g/km in 2018. By the end of this year, this number needs to come own to 95g/km under EU regulation. Failing to reach the target equals bankruptcy-scale fines for the OEMs. And let's not forget that 95g is just an intermediate step. By 2025, carbon dioxide levels have to come down by another 15% compared to the 2021 levels and five years later, 37.5% is shaved off of the target values. These targets were set in 2018, but with the new Green Deal, they may be adjusted.

Going down from 120 to 95g in 2020 seems like an impossible task, but most carmakers seem rather confident nonetheless. They are putting their hopes in plug-in hybrid powertrains in 2020, a year that will see a tsunami of new PHEV models on the European market, from the Renault Captur E-Tech all the way through to the Land Rover Defender.

Still, that won’t suffice, especially not for those that sell heavy crossovers and SUVs. They simply can’t do without diesel today. If anything, the introduction of WLTP is playing in the hand of diesel. Indeed, self-combusting engines remain 20 to 25 percent more fuel efficient than their petrol peers and are often the only powertrain that fits in CO2-capped vehicle categories that most large corporates apply.

BMW: d alongside e

Especially premium car makers have found salvation in the electrification of their line-up. BMW promises to have up to 25 plug-in hybrid and all-electric models in its line-up by 2025. In 2018, the Bavarian OEM delivered 75,000 vehicles with an electric motor in Europe – most of which mated to a combustion engine. The Old Continent is BMW’s biggest sales region for battery and plug-in hybrid vehicles, accounting for over 50% of its global e-sales in 2018.  

However, Munich still believes in diesel, too. For decades, the letter d has been the synonym for class-leading fuel efficiency, low emissions, smooth performance and high residual values. BMW has no intention of letting this technological heritage and competitive advantage go to waste, as demonstrated by recent ADAC emission tests. BMW has succeeded in reducing NOx emissions of its latest diesels to levels way below the Euro 6d-temp limit, making them ultra-clean and doing away with the argument that there is no place for diesel in cities because of their emissions.

Mercedes: d and e in one

If diesel engines still (and always will) produce less carbon dioxide emissions, why not combine d with e to maximise efficiency? The concept is not new: Volvo launched the V60 D5 Twin Engine back in 2012, offering an electric range of 50 km and limiting its CO2 output to just 49 g/km. The recipe was copied by Audi in 2015, when the Q7 E-tron was introduced.

The idea was to combine the characteristics of a long-distance cruiser with those of an emission-free urban vehicle. You burn diesel on the motorway and save the battery for city driving. Most OEMs have opted for petrol for their (P)HEV models – long before dieselgate, incidentally – because they found it hard to reconcile diesel noise and vibrations with utter electric silence.

Mercedes persists in the belief that it makes sense to electrify diesels. They have never been cleaner, more refined or more efficient. Moreover, they can cope better with the extra weight that comes with the battery pack. The brand-new C 300 de, for instance, combines the 220d’s engine with a 13.5 kWh-battery allowing it to travel 57 km on electricity alone and emit 42 g/km of CO2 (NEDC correlated). The new GLE 350 de even has a 31.2kWh battery for roughly 100km of electric range and a CO2 rating of 29g/km.

Diesel is futureproof

It seems that thanks to today's and tomorrow's emission targets and WLTP, diesel cars are here to stay for another decade, even though some OEMs have announced they will stop making them already in 2025.

With production costs increasing due to the ever stricter emission regulations and taxes privileging petrol in many countries, it stands to reason that the oily fuel will be confined to the C-segment and above.

Especially heavy and/or bulky cars (i.e. SUVs) are better off with diesel, not least from a fuel consumption point of view: weight and air resistance have less impact on the fuel efficiency and hence CO2 emissions of a torquey diesel than on those of a sparky petrol engine.  

Recent sales data show the diesel share in Europe is expected to flatten out at 30%. That might even create a shortage on the used car market, which is still quite fond of cars with a TDI, d, HDi and CDTi badge. Some say this could positively effect diesel residual values in the coming years. And that’s good news for the TCO.

As to the eco credentials of the fuel: recent research by Air Alliance and ADAC indicates that the carmakers really have done their homework. The Mercedes C 220 d even got a rating of 10 out of 10 from GreenNCAP, making it as clean as an all-electric car - if you take a holistic look.

Authored by: Dieter Quartier