What is WLTP (worldwide harmonised light vehicle test procedure)?

WLTP (worldwide harmonised light vehicle test procedure) is a testing standard used to measure fuel economy and emissions. WLTP began its introduction in 2018, replacing the older NEDC testing standard, and is intended to be a more accurate measure of real-world efficiency. This is why advertised mpg figures for comparable cars got worse after 2018, because they were being measured according to this newer, stricter standard.