20 Aug 17

WLTP will reshuffle the EU fuel consumption cards

Per September 1st, the Worldwide harmonized Light vehicles Test Procedure (WLTP) replaces the New European Driving Cycle (NEDC) as the mandatory type approval procedure for fuel consumption and CO2 emission figures for new cars in Europe. A fiscal disaster, or an opportunity in the making?

Fuel consumption and CO2 emission numbers currently published by manufacturers are based on the NEDC or New European Driving Cycle – the origins of which go back to the 1980s, when nearly all engines were classical combustion engines, roads were relatively empty and people used their vehicles in an entirely different way from today. The main purpose of NEDC was to ensure comparability of results: if every OEM uses the same method, results can be compared objectively. 

With cars and their drivers having changed considerably over the past decades, NEDC has become tremendously unrealistic, leading to considerable discrepancies between official and real-life fuel consumption. Moreover, the NEDC method does not describe the testing method and parameters in detail, giving OEMs the freedom to use ‘dirty little tricks’ to save a few centilitres and grams – such as using special lubricants, disconnecting the alternator, etcetera. 

NEDC: an OEM’s friend

Especially plug-in hybrids ‘benefit’ from NEDC because they can travel large portions of the test cycle on electricity alone. Carbon dioxide (CO2) is nothing but a function of fuel consumption, incidentally. As one litre of petrol weighs 750 grams and 87 percent of petrol consists of carbon (C), this volume corresponds to 652 grams. You need 1740 grams of oxygen (O) to burn this quantity, resulting in 2392 grams of CO2 per 100 kilometres, or nearly 24 grams per kilometre.  

OEMs have been developing their powertrains with this unrealistic NEDC in mind, with long 5th and 6th gears, start-stop systems and so on, which make a car look good on paper, but not necessarily in real life. That is about to change. Consumer organisations and environmental stakeholders have been pushing for years for a more realistic way of measuring how much fuel a car uses. The result is WLTP.

WLTP: a consumer’s friend

WLTP, or Worldwide Harmonized Light-Duty Vehicles Test Procedure, becomes the official EU type approval method in September 2017. It is still is a lab test – during which a vehicle is put on a dynamometer, to exclude as much variables as possible – but it takes into account higher average and maximum speeds, more realistic outside temperatures, faster acceleration and greater test distances. Last but not least, the influence of optional equipment is also measured.  

The procedure has been developed using a multitude of real-life driving profiles from all over the globe, allowing to simulate an average car ride in a laboratory. The tests consist of four stages, each with a different average speed: slow, medium, high and very high. During every phase, the car accelerates and decelerates many times according to a fixed scenario. The entire cycle takes about half an hour. The NEDC only lasts 20 minutes. 

Beneficial to fleets?

WLTP allows fleets to better budget the amount of fuel their vehicles use. That’s the good news. The bad news is that WLTP leads to higher CO2 levels and therefore higher taxation in countries applying an emission-based system – unless the tax bands are adapted. But what if they are not? “It is impossible to know what the difference between NEDC and WLTP figures will be, but the fiscal impact could be considerable”, says an Opel official in the European Fleet Team.

In conclusion, WLTP might reshuffle the cards in OEM land, privileging those who develop cars that consume the least in real-world conditions rather than in manipulated lab set ups. It might also accelerate the development of electrified powertrains, evidently.

Authored by: Dieter Quartier