Emissions are the result of the combustion of fuels such as natural gas, gasoline, petrol, biodiesel blends, diesel fuel, fuel oil, or coal.
A new report has revealed that diesel cars on UK roads are even more polluting than previously believed, with some cars 11 times beyond the legal limit.
Tests by consumer organisation Which? have found that the majority of new diesel cars still exceed the new emissions limits in "real-world" testing.
Motorists could be burning through as much as 75% more fuel than stated by car makers, according to new research by German technology company Carly.
WLTP is a new fuel economy and emissions testing system that gives car buyers a more accurate picture of how their new car will perform in the real world.
The UK government has announced that it will ban the sale of new petrol and diesel cars from 2040. But is that realistic for an electrified car market?
Mercedes-Benz and Audi have announced recalls for nearly four million diesel cars across Europe in a bid to avoid fines and vehicle bans in European cities.