Report finds WLTP hugely over-estimates car fuel economy

The car industry is facing a possible crisis concerning real-world fuel economy data – which could have wide-ranging repercussions as significant as the fallout from the Dieselgate emissions test cheating scandal.

Two reports have emerged from the European Union over the past few weeks, the latest from the European Commission, and both could have far-reaching effects on the type of vehicles that manufacturers will be selling as soon as 2026.

What has happened?

The European Court of Auditors and the European Commission both say the first real-world data obtained on fuel consumption shows that petrol, diesel and plug-in hybrid cars are all well adrift of their official laboratory calculated fuel consumption and CO2 emission figures.

The first estimates for a sample of cars registered in 2022 show that the WLTP test regime overestimates the fuel economy of petrol cars by 23.7% and of diesel cars by 18.1%.

PHEVs average CO2 emissions of 139.5g/km, which is some 23% better than the internal combustion engine average.

However, the real-world monitoring suggests that PHEVs aren’t being charged as often as was estimated by the WLTP regime.

The upshot of the analysis is that larger-engined models, the heaviest SUVs and luxury cars and PHEVs, along with underperforming mainstream ICE vehicles, will now face renewed scrutiny by the European authorities.

The EU Court of Auditors also recommends that the EU follows the UK’s legislative lead and drops the current laws that make car makers meet ‘fleet average’ CO2 targets (currently 115.1g/km, dropping to 93.6g/km from next year) in favour of “targets based instead on a minimum share of zero-emission vehicles”.

Although the UK market is no longer directly affected by EU CO2 fleet average laws, 53% of cars made in the UK are exported to the EU market, so British car makers’ offerings will remain under scrutiny.

What went wrong?

After Dieselgate, the EU moved to replace the standardised New European Driving Cycle (NEDC) laboratory fuel economy tests, which dated back to 1992, with a new economy test format.

The Worldwide Harmonised Light Vehicles Test Procedure (WLTP) then arrived in 2017. The WLTP test cycle was longer (30 minutes instead of 20 minutes), conducted over a greater distance (14 miles instead of six miles), included less stopping, took in higher average speeds and required greater levels of acceleration.

Assurances were given that the WLTP driving cycle “was based on a global statistical survey of real driving profiles”, but new in-car technology quietly deployed by the EU in new cars since 2021 has now proved the test to be significantly overestimating cars’ real-world economy.