What is CO2 emissions from cars?

The amount of carbon dioxide, also called CO2, that your car produces directly impacts your wallet. And it has also become a political issue as governments around the world pass laws to address the climate change crisis. But why does your car emit CO2 at all? Why does it cost you money? And is there anything you can do to reduce your CO2 emissions while driving? Kazu explains.

Why does my car emit CO2?

Most cars on the road have a gasoline or diesel engine. The fuel is mixed with air and burned in the engine to generate energy that powers the vehicle. Burning anything produces gas as a waste by-product. Gasoline and diesel contain a lot of carbon, so when they are burned, they produce waste in the form of carbon dioxide. A lot of everything. It is blown out of the engine and through the exhaust pipe. As it exits the pipe, CO2 is released into our atmosphere.

How are CO2 emissions measured?

The fuel economy and CO2 emissions of all vehicles are measured before they go on sale. The measurements come from a series of complex tests. The results of these tests are published as "official" data on fuel economy and CO2 emissions.

You can read more about how the official MPG value of a car is calculated here.

A vehicle's CO2 emissions are measured at the tailpipe and calculated from the amount of fuel used during testing using a complex system of equations. Emissions are then reported in units of g/km - grams per kilometer.

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How does my car's CO2 emissions affect my wallet?

Since 2004, annual road taxes on all new cars sold in the UK and many other countries have been based on how much CO2 the cars emit. The idea is to encourage people to buy cars with less CO2 emissions and punish those who buy cars with more CO2 emissions.

The amount of tax you pay depends on which CO2 "range" your vehicle belongs to. Owners of cars in lower lane A don't have to pay anything (although you still have to go through the process of "buying" road tax from the DVLA). Cars in the top group are charged a few hundred pounds per year.

In 2017, the lanes changed, resulting in an increase in road tax for most vehicles. The changes do not apply to cars registered before April 1, 2017.

How can I find out my car's CO2 emissions?

You can find out the CO2 emissions of a car you already own and what tax group it is in from the V5C registration document. If you want to know the CO2 emissions and road tax cost of the car you want to buy, there are a number of "calculator" websites. In most cases, you simply enter the vehicle's registration number and you will be shown the details for that particular vehicle.

Cazoo informs you about CO2 emission levels and road tax costs in the information we provide for each of our vehicles. Just scroll down to the Running Expenses section to find them.

It is worth noting that the road tax for vehicles registered after April 1, 2017 actually decreases as the vehicle ages. And there are additional fees if the car cost over £40,000 when it was new. If that sounds complicated, it is! Watch for a road tax reminder that will be sent to you by the DVLA approximately one month before your vehicle's current road tax expires. He will tell you exactly how much the renewal will cost.

What is considered a “good” level of CO2 emissions for a car?

Anything less than 100g/km can be considered low or good CO2 emissions. Vehicles with a mileage of 99 g/km or less, registered before April 1, 2017, are not subject to road tax. All petrol and diesel vehicles registered after April 1, 2017 are subject to road tax, no matter how low their emissions are.

Which cars produce the least CO2?

Diesel vehicles produce much less CO2 than gasoline vehicles. This is because diesel fuel has a different chemical composition than gasoline and diesel engines burn their fuel more efficiently. 

Conventional hybrid cars (also known as self-charging hybrids) typically produce very little CO2 because they can run on electricity for a while. Plug-in hybrids have very low CO2 emissions because they have a much longer range on electricity alone. Electric vehicles do not produce carbon dioxide emissions, which is why they are sometimes referred to as zero-emission vehicles.

How can I reduce CO2 emissions in my car?

The amount of CO2 your car produces is directly proportional to fuel consumption. So making sure your car uses as little fuel as possible is the best way to cut CO2 emissions.

Engines consume more fuel the more they have to work. And there are plenty of simple life hacks to keep your car engine from overworking. Keep windows closed while driving. Removing empty roof racks. Inflating tires to the correct pressure. Using as little electrical equipment as possible. Timely vehicle maintenance. And, most importantly, smooth acceleration and braking.

The only way to keep a car's CO2 emissions below official figures is to fit smaller wheels. For example, a Mercedes E-Class with 20-inch wheels emits several g/km more CO2 than 17-inch wheels. This is because the engine has to work harder to turn the larger wheel. But there may be technical issues that prevent you from fitting smaller wheels - such as the size of the car's brakes. And your road tax bill won't go down if you can't reclassify your car.  

Cazoo has a variety of high quality, low emission vehicles. Use the search function to find the one you like, buy it online and have it delivered to your door or pick it up at your nearest Cazoo customer service center.

We are constantly updating and expanding our range. If you can't find one today, check back soon to see what's available, or set up a stock alert to be the first to know when we have cars that match your needs.