The Worldwide Harmonised Light Vehicle Test Procedure (WLTP) was meant to bring CO2 emissions in line with the real-world by more closely replicating actual vehicle use in laboratory tests, but while real-world diesel car CO2 emissions are now close to the latest laboratory results, tests of petrol cars and real emissions appear to vary widely.

Emissions Analytics is claiming WLTP tested vehicles average of 133g/km, yet the real-world average CO2 figure, as measured by Emissions Analytics, is, in fact, 185g/km. This anomaly raises concerns that while car makers have got their houses in order over diesel they may still be ‘optimising’ vehicles for official lab tests.

Intended to address the shortfalls of the discredited New European Driving Cycle (NEDC), the Worldwide Harmonised Light Vehicle Test Procedure (WLTP) was supposed to bring CO2 figures in line with actual vehicle use and give consumers clarity. CO2 values for diesel cars have risen, as would be expected for a tougher test, between NEDC and WLTP. The average WLTP result of 175 g/km CO2 is very close to the Emissions Analytics’ real-world average figure of 173 g/km.

Petrol cars, on the other hand, fell, counterintuitively, under the new test. The WLTP average figure was 151g/km compared to 152g/km under the NEDC. The NEDC-equivalent value, the one used to determine fleet averages, was even lower at 133g/km. All these values still lie far below the real-world figure of 185g/km measured by Emissions Analytics.

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