Pollutionwatch: exhaust emissions double below 20C – by design

Modern cars can start in the cold, so why are manufacturers failing to make exhaust controls more efficient below 20C?

Twenty-five years ago, starting a car in winter required careful balancing of choke and accelerator and sometimes sprays of WD40 or a bump start. Now, modern vehicles simply work in the cold. However, a European parliament inquiry following the Volkswagen scandal found that the nitrogen oxides abatement systems on many diesel cars shut down below the official test temperature of 20C. Manufacturers say that this prevents engine damage and is therefore legal. Real-world driving measurements on 9,000 cars in Gothenburg, Sweden, have shown this shutdown in action. Average emissions at 10C were almost twice those at 25C.

Related: What is behind the diesel cars emissions scandal?