CO2 (carbon dioxide)
When fuels such as petrol and diesel, are combusted carbon dioxide (CO2) is produced and released into the atmosphere. CO2 is believed to be a major contributor to global warming so vehicle makers have been set tough limits to meet by 2020 – 95g/km.

DPF (diesel particulate filter)
A diesel particulate filter is fitted to the exhaust of all Euro-5 and Euro-6 cars. It traps 99% of all particulates emitted by the exhaust, making its PM emissions significantly lower than older cars.

Euro 6
Euro 6 (referred to as Euro VI for heavy commercial vehicles) is the most recent regulation for vehicles sold in Europe to ensure the cleanest engines. Since 1993, the European Commission has enforced a Euro standard of emissions, which all vehicles on sale must meet.

NEDC (New European Driving Cycle)
Until September 2017, all new cars had their emissions measured by the NEDC, the EUs previous official emissions test for cars. The test was operated in strict laboratory conditions and, like the new test (WLTP), was monitored by a government-appointed independent approval agency. In the UK, this is the Vehicle Certification Agency.

NOx refers to nitrogen oxides or oxides of nitrogen, and is a by-product of fuel combustion. When measuring emissions, these are known as oxides of nitrogen, or NOx.

Particulate matter (PM) or Particulate Number (PN) 
Particulate matter, better known as soot, is a waste material of combustion. Thanks to a filter that captures 99% of exhaust particulates; Euro 6 diesel cars emit the equivalent of a single grain of sand in PM each kilometre.

PEMS or portable emissions measurement system is a mobile laboratory which measures and analyses tailpipe emissions on the move. It is used in new Real Driving Emissions tests, introduced from 1 September 2018.

RDE stands for Real Driving Emissions, and refers to the emissions test that a car will be expected to comply with when tested on the road rather than in a controlled laboratory environment. This can be affected by many different conditions including car condition, weather conditions, driving style. A new RDE test for new cars has now been introduced, which measures ‘real world’ emissions performance.

Selective catalytic reduction is an emission reducing technology used in diesel cars. This specialist catalytic converter injects a chemical called AdBlue into the exhaust to convert NO­X into nitrogen and water.

The Worldwide harmonized Light vehicles Test Procedure (WLTP) is a new test cycle, introduced from 1 September 2017. It is much more comprehensive and challenging than the NEDC and is based on real driving data to ensure results better reflect those achieved by consumers on the road.