Consumption and emissions. What is that?

Setting a vehicle in motion requires energy. Conventional powertrains burn fuel in order to convert heat into kinetic energy. Depending on the design of the combustion engine, the size and weight of the vehicle as well as the driver’s driving style, there is a variation in the required quantity of fuel, the energy content of which is released by combustion. There is a direct correlation between the amount of fuel burned and the arising CO₂ emissions – the higher the fuel consumption, the higher the quantity of carbon dioxide emissions. In addition, there is a direct correlation between many comfort/safety functions and fuel consumption.

Quantity of fuel consumed and cleanliness of combustion.

Apart from CO₂ emissions, other constituents of the exhaust gas are of relevance. This refers in particular to NOx (nitrogen oxides) and particulate emissions, which are taken into account in the assessment of modern diesel and petrol direct-injection engines. A distinction is made between the quantity of fuel consumed (CO₂ emissions) and the cleanliness of combustion (NOx, particulates).

Real Driving Emissions (RDE).

Real Driving Emissions (RDE) describe a vehicle’s emissions under real on-road conditions. To date, exhaust emissions measurements for type approval have taken place exclusively on dynamometers. With effect from March 2016, within defined limits, emissions must also be measured under real driving conditions.The RDE on-road test verifies whether the values determined in the laboratory are also met under real, vehicle-specific driving conditions. There is no set cycle; driving and measuring take place in real everyday traffic in compliance with the rules of the road. Together with the WLTP values communicated from September 2017, this represents a further important step towards a cleaner and less-polluting automotive future.

Tested under everyday conditions.

The RDE test procedure measures the exhaust emissions in a road test conducted under everyday conditions. The goal of the legislation is to cover 95 % of possible operating conditions. A PEMS (Portable Emissions Measurement System) is used to measure nitrogen oxide (NOx) and carbon monoxide (CO) emissions. At a later date, particulate emissions will also be measured. The vehicles are driven on public roads for between 90 and 120 minutes, approximately one third each on urban and extra-urban roads and on the motorway. An average speed of between 15 and 30 km/h is specified for city driving, while the speed on motorways is 90 and at least 110, but not higher than 145 km/h. The outside temperature must be between 0 and 30 °C, with the air conditioner on.

Requesting the RDE results.

The RDE results of Mercedes-Benz vehicles, which were collected both by Mercedes-Benz as the manufacturer and also by independent, state-certified technical services, can be requested using a contact form while stating the PEMS test family of the relevant Mercedes-Benz vehicle.

Contact form for RDE results

The PEMS test family number of the vehicle is available on the homepage of the European Automobile Manufacturers’ Association (ACEA).