Mercedes are accused of deceiving authorities and customers by fitting millions of their diesel cars with "defeat devices" or "cheat devices" that show a lower reading on emissions tests than what were actually being released into the atmosphere. The lower test readings brought about from these devices allowed the diesel cars to pass strict emissions tests and be deemed road legal, without these devices the cars would not have passed and therefore not be road legal in the UK. This has affected the resale value of the car and caused more polution for the environment when consumers might have based their buying decision on environmental factors. You might have heard about the Volkswagon diesel emissions case, lawyers say, that whilst the device used is not the same it is similar in the effect it is hoping to achieve - deceive regulators and customers that the car is more environmentally friendly and more efficient than it really is.