The same car suddenly has two different CO2 values, why is this?

The new Worldwide Harmonised Light Vehicle Test Procedure (WLTP) is a new and more robust test cycle for cars, and therefore has higher (but more realistic) CO2 and fuel consumption values.

  • Before September 2017, all cars at dealerships had CO2 values based on the old NEDC test (the New European Driving Cycle).
  • During the period of transition from NEDC to WLTP that started in September 2017, cars approved before then will continue to have CO2 values as measured under the NEDC test only.
  • However, when a new car type is certified under WLTP after September 2017, its official vehicle documents (the Certificate of Conformity) will have CO2 emission values from both the new lab test as well as the old one.
  • From September 2018, all new cars must have WLTP-CO2 values


This means that after September 2017, when the switch from the NEDC to WLTP is being made, one might come across two different values for the same car. This risks being quite confusing, making it difficult to compare cars.

A very important issue therefore is how WLTP will be integrated in car labelling and other consumer information.

Transition Timeline: From NEDC to WLTP

  • Cars type approved using NEDC before September 2017 can still be sold.
  • WLTP type approval testing will be introduced for new car types.
  • Some cars will have ‘old’ NEDC values, while others will already be certified under the new WLTP conditions.
  • The industry would like to start using WLTP-based results for general consumer information (eg sales brochures and websites).
  • During the period of transition (up until the end of 2018), only NEDC values should be used on labels and information in dealerships to enable consumers to compare different cars.
  • It is expected that national tax regulations will continue to be based on NEDC values.

The same car suddenly has two different CO2 values, why is this?

The NEDC value of a car suddenly increased, what happened?

  • All new cars must be certified according to the WLTP test procedure, and no longer on NEDC.

Will my fuel consumption increase under WLTP?

  • All cars in dealerships should have WLTP-CO2 values only to avoid any confusion among consumers, in the view of the automobile industry.
  • An exception will be made for end-of-series vehicles to allow for a limited number of unsold vehicles in stock that were approved under the old NEDC test to be sold for one more year.
  • National governments should adjust vehicle taxation and fiscal incentives to WLTP values, respecting the principle that WLTP should not have a negative impact on consumers.

Will WLTP affect how much car tax I pay?

The same car suddenly has two different CO2 values, why is this?

  • The European Commission will convert today’s (NEDC-based) CO2 targets to specific WLTP-CO2 targets of comparable stringency. These new WLTP targets will apply for monitoring car fleet compliance.

Will the new WLTP test affect CO2 targets?

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