Although the car market is moving towards fully electric models we know that not every driver is ready or able to, because of their vehicle requirements. Here at Wessex Fleet we think it’s important to understand about the impact of your fuel type choice, and so we’ve put together this guide to CO2 to help you understand the gas, why it’s important and the impact it can have when deciding your next company car.

What is CO2?

Carbon dioxide, CO2, is a gas in the Earth’s atmosphere, that occurs naturally but can also be emitted as a pollutant by a host of different activities, the most common of which is the burning of fossil fuels.

Naturally occurring levels of CO2 are balanced in the Earth’s atmosphere by natural processes like plants absorbing it through the photosynthesis process. However, as humanity has industrialised and we have increased the activities that produce more CO2 whilst reducing the amount of vegetation and its mitigating effect.

One of the biggest ways that individuals contribute to CO2 emissions is through driving vehicles with traditional combustion engines which emit pollutants including CO2.

Other Emissions

Vehicles do not only emit CO2 but also a number of other pollutants including carbon monoxide, nitrogen oxide, nitric oxide, hydrocarbons and particulates like soot.

We’ve taken a more in-depth look at these and what they mean in the petrol and diesel guides we have, but the most important emission is generally considered to be C02.

These emissions are tested to Real Driving Emissions (RDE) testing and Euro 6 standards.

Why Should I Care about CO2 Emissions?

There are a number of reasons for you to look at the CO2 emissions of a vehicle when deciding if a model is right for you, and these include road tax, company car taxMOT testingair pollution and Low Emission Zones (LEZs)

CO2 and Road Tax

The amount of road tax you pay for a vehicle is based on the amount of CO2 it emits, so if you are liable for paying the road tax on a vehicle the lower CO2 emissions your car has the lower the road tax.

With most company cars it will usually be the business who covers the road tax, and so while this might not have as much of a direct impact on your choice you might find that you’re directed towards lower emission vehicles.

CO2 and Company Car Tax

If you are a driver who uses a company car and is required to pay company car tax then you will want to carefully consider the CO2 emission levels of any model you are interested in as this is factored into the amount of company car tax you will have to pay.

Company car tax is calculated by finding the company car tax rate, which is based on the CO2 emissions, then multiplying this by the P11D value of the vehicle which gives you the benefit in kind (BIK) amount. To find out how much you will need to pay you then need to multiply the BIK amount by your personal tax rate and this will give you the annual figure.

For a more detailed look at company car tax then take a look at this guide

CO2 and MOTs

If the car you are driving is over three years old then it will need to have an MOT annually. As part of the MOT testing the emission levels of the vehicle will be tested and if they exceed the allowed levels then it will fail the MOT and be undrivable until necessary repairs are completed.

Again, if you have a company car then this might not be as big of a concern for you as this will usually be covered by the business depending on the company car scheme they offer.

CO2 and Air Pollution

The amount of CO2 a vehicle emits not only affects the global air quality but also in your local environment where you are regularly driving. Depending on where you live there may be restrictions on the amount your vehicle can pollute or a fee for driving a higher emitting vehicle.

Low Emission Zones

Many towns and cities across the UK are introducing LEZs and Clean Air Zones (CAZs) to help reduce pollution and improve air quality in their city centre. These zones can place restrictions on the vehicles that can enter, what areas vehicles are allowed and even putting a fee and fine system in place for vehicles that enter particular areas.

With this becoming an increasingly popular strategy to improve air quality you’ll want to check your local area and the towns and cities you frequently visit to see what plans they have for putting in place such a zone.

The RAC have this useful map that shows all the active clear air schemes across the UK.

With these zones lower-emitting vehicles will fair better.


Emission Testing

New vehicle models are vigorously tested and heavily regulated to ensure that the vehicles meet modern emission standards as manufacturers meet national and global restrictions on vehicle emission levels.

CO2 is measured by its weight in grams and for measuring how much a vehicle emits the universal measurement is given in grams per kilometre, so you’ll see g/km when looking at CO2 levels.

In the UK the current target is 95 g/km.

WLTP Testing

The main way that new vehicles are tested for CO2 emission levels for the UK market is with World Harmonized Light-Duty Vehicle Test Procedure (WLTP) testing. 

WLTP testing was introduced as there were worries over previous testing methods not reflecting real world driving conditions and so giving inaccurate emission levels. Vehicles are tested in a dynamic cycle that is designed to simulate real driving conditions, with the cycle lasting 30 minutes and covers 23.23 km distance during this. It includes four driving phases with low, medium, high and extra-high speeds, with an average speed of 46.5 km and a maximum speed of 131 km per hour, which is split between urban and non-urban driving conditions.

As the name suggests WLTP is designed to be a universal measurement system across brands around the world so that drivers can easily compare between brands.

Your CO2 FAQs Answered

Why Does My Car Produce CO2?

CO2 is produced as a byproduct of the internal combustion engine within your car, this is not needed to power the vehicle and so the gas is released as part of the vehicle's emissions. 

All vehicles with a combustion engine (petrol, diesel and hybrids) will produce CO2 emissions. 

How Are CO2 Emissions Measured?

For vehicles CO2 emissions are measured in the weight of CO2 emitted over a kilometre, so the measurement will be given in grams per kilometre (g/km). 

When a manufacturer produces a new model it will go through vigorous testing, including emissions testing to make sure that it meets the requirements of the countries it will be sold in. 

Additionally once a vehicle has been sold and reaches three years old it will be tested annually to make sure it is below the limit allowed by UK law. If it exceeds this it will fail the MOT and work will need to be completed to reduce the vehicles emissions before it can legally be driven. 

How Do I Find Out How Much CO2 My Car Produces?

You can find out how much CO2 your vehicle produces on the government's website here where they break down the CO2 emission levels of each model.

Additionally, when your vehicle goes in for its MOT the testing garage may provide you with a copy of the emission test results which will show your level. 

What's An Acceptable CO2 Emission Level For a Car?

Generally, any vehicle that emits below 100 g/km is considered to be a low polluting vehicle which we think is an acceptable level for a modern car. New vehicles have a target of 95 g/km so will be under this already but older models (pre 2021) will not have had to meet this standard. 

We'd say that for a car produced in the last 20 years emissions of under 130 g/km is a good level. 

How Can I Reduce My Car's CO2 Emissions?

There are a few things you can do to reduce your CO2 emissions and they include:

  • Use a tank of premium fuel every so often
  • Add a cleaning agent to the fuel tank every so often
  • Make sure your tyre pressure is at the optimum pressure
  • Change your oil
  • Change the air filters
  • Keep your use of the air conditioning to a minimum

These tips will also help you with improved fuel economy.

Reducing CO2 Emissions

There are a few things you can do when driving a petrol or diesel vehicle to help reduce the emissions they produce but we’ve rounded up Wessex Fleet’s top five tips below:

1. Keep up to date with the vehicle servicing

2. Remove any roof and bike racks when not in use

3. Drive carefully and avoid harsh acceleration and braking

4. Don’t sit with the engine running

5. Regularly check the tyre pressure and keep at the optimum level

If you're looking to go greener and reduce your CO2 emissions completely then an electric vehicle would be the best choice for your next car. You might also want to consider looking at a hybrid model if you’re not ready to go fully electric yet as they can offer the best of both worlds. For more information on hybrid models and the different types available then take a look at this guide

If you have any questions about the CO2 of your company vehicle and how this affects you get in touch on 01722 322 888.


Contact Wessex Fleet