Cars that Produce the Most CO
Air pollution from diesel cars might be making the headlines - but that doesn't mean that petrol cars are innocent.
While petrol cars produce very little in the way of NOx (apart from a very small number, see our round-up of the cars that produce the most NOx), petrol cars do produce carbon monoxide (CO) in large quantities.
Our carbon monoxide emissions tests have revealed:
A quarter of modern petrol cars in our tests produced more CO than would be officially allowed in 1993
This includes three petrol-hybrid cars.
Keep reading to find out more about our tests and to discover which cars produced the most CO emissions in them.
If we find a car with very high CO emissions, we won't make them Best Buys. To find your next car that doesn't have massive amounts of emissions, head for our best cars.
CO emissions explained
Carbon monoxide (CO) is a colourless, odourless and highly toxic gas. The risk of suffering ill effects from the amount of CO produced by cars is very low (unless the car is running in an enclosed space, such as a garage), but CO itself can be fatal. CO, just like NOx, is one of the gasses limited by emission laws.
Euro emissions laws limit the amount of CO cars can produce (in official test conditions). This started with CO being limited to 2.72g/km in 1993 when Euro 1 was introduced. Years later when Euro 2 replaced Euro 1, the limit was dropped to 2.2g/km. We are currently on Euro 6 and the limit is 1g/km of CO.
In our tests, 30% of petrol cars failed to meet Euro 4/5/6 standards (the CO limit has not changed since Euro 4). Even more surprisingly, 24% emit more CO emissions than the Euro 1 limits from 1993.
Carbon dioxide (CO2) is a different gas that is much more harmful to the environment than to people or animals. There’s been some confusion in the media between CO2 and the other emissions. But it’s best to think of CO2, which is primarily bad for the environment, as separate from CO and other emissions including NOx, which are particularly bad for human health.