We’ve put together a collection of handy guides for drivers looking to compare fuel types to decide what the right choice for them is and you can see them all here. This guide will focus on diesel fuel, the benefits and drawbacks of it, the environmental impacts, tax implications and how to decide if it’s the right choice for you.

What is Diesel Fuel?

Diesel is one of the two main fossil fuels that are used in vehicles, the other being petrol, and is used to power the combustion engine in your car.

Over the years diesel has been in and out of favour with manufacturers, drivers and governments alike so it’s understandable if you’re unsure whether you should opt for diesel with your next company car. In this guide, we’ll explore all the reasons that diesel could be right for you and considerations you need to make to help you decide whether or not it is the best choice for you.

The Benefits of Diesel Fuel

Diesel became a popular choice in the late 1990s to early 2000s because it was found they emit less CO2 into the atmosphere as part of their exhaust emissions. This is still true to this day, that mile for mile diesel emits less CO2 than their petrol equivalents. However, they have higher levels of other harmful emissions which we’ll look at later.

Diesel offers drivers better fuel economy than a tank full of petrol and does not require charging like an electric vehicle. So, if you are regularly doing long distance driving and have a high annual mileage then diesel might be the best option. Though the cost of a tank of diesel is more expensive at the pump because it offers better fuel economy it usually works out to be cheaper for you over the vehicle’s lifetime rather than a petrol version.

Typically, diesel engines will be larger than the petrol ones in an equivalent model, and this means they are more powerful so able to achieve a greater torque. Greater torque gives you better overtaking power and more towing capacity. For drivers who are often towing a trailer then a diesel engine will probably be a better choice.


Pricewise, diesel will usually be cheaper than hybrid or electric models as there are not as many expensive electronics involved in their construction.

Things to Consider with a Diesel Vehicle

Now that we’ve gone over the benefits there are a few other considerations you need to make when deciding if diesel is the right option for you.

Diesel vehicles are typically pricier than their petrol counterparts, so the purchase or lease price will be higher. If you are driving a company car then you will need to consider the company car allowance you have been given and whether the model you are looking at fits within this.

You might also find that servicing and maintenance costs are a little higher with a diesel engine as there are additional components such as the diesel particulate filter (DPF) that a petrol car will not have.

The DPF helps reduce the emissions your vehicle makes, which is important as they do emit higher levels of harmful pollutants. However, it also requires a particular style of driving to prevent the filter from becoming clogged and the costly expense of replacing this. It will need to be driven regularly on a high-speed road.

If you mainly drive on constant, low-speed urban areas then diesel will not be a good choice for you as the DPF will become clogged quicker with this type of driving.

For drivers concerned about fuel economy as diesel is a more expensive fuel then you might want to take a look at our tips here

Another thing you’ll want to consider is low emission zones. Many towns and cities are introducing low emission zones, clean air zones and even zero emission zones to help them meet emission targets and improve the air quality in their area. We recommend checking whether where you live or work is looking to introduce these areas, as typically a diesel car will pay a higher tariff to enter, or eventually be banned from driving through the city centre.

If you live in an area where the council has a parking permit scheme active then you will want to check that they don’t apply a diesel surcharge. Some local authorities charge a higher permit rate for diesel vehicles to discourage residents from driving them.


Diesel and the Environment

Over the years we’ve all learnt more about the environment and how particular activities that we do every day has an impact. Perhaps one of the biggest impacts individuals have is through their driving, in particular the vehicles they choose to drive.

Although modern diesel engines are much cleaner than diesel cars of the past, they are still the least environmentally friendly of the engine options available for you to choose from.

We mentioned earlier that diesel cars produce les CO2 than the petrol equivalent, but they instead emit higher levels of other pollutants like nitrogen oxide. These higher levels of pollutants are why a DPF is fitted to all diesel exhaust systems, as it helps reduce them.

Additionally, most modern diesel vehicles now have technology that converts most of the nitrogen oxide into nitrogen and oxygen, both of which are harmless to the environment.

There are currently two emission standards that diesel vehicles are measured up to.

The first is the Euro 6 emission standards, which were introduced in 2015. These are designed to place more stringent restrictions on vehicles than the previous Euro 5 standards.

Many emission zones, congestion charges and European countries might have restrictions or increased charges for higher polluting or diesel vehicles.

Euro 6 Standards

Current Euro 6 emission standards for a diesel engine are:

CO: 0.50g/km

HC + NOx: 0.17g/km

NOx: 0.08g/km

PM: 0.005g/km

PN [#/km]: 6.0x10 ^11/km

The second standard of testing used in the UK is the Real Driving Emissions (RDE) testing, where the vehicle will be tested under real-world driving conditions in order to provide a more accurate representation of emission levels.

These tests were introduced in 2017 and in 2019 became mandatory for all new vehicles being sold in the UK.

There are currently two stages of RDE testing: RDE1 and RDE2.

RDE1 allows a car to emit 2.1 times the amount of nitrogen oxide than that allowed in laboratory testing conditions and RDE2 allows them to emit just 1.5 times the amount. All vehicles must now be compliant with RDE2 standards in order to be sold in the UK.

Tax on Diesel Vehicles

If you are looking to purchase your next vehicle yourself then you need to be aware that a diesel car will usually come with a higher road tax. This is especially the case if the vehicle is not RDE2 compliant.

If you are leasing the vehicle personally then you also need to bear this in mind. The lease funder will cover the cost of road tax at the price the vehicle was first taxed, so if there is an increase to the amount payable you might be required to pay the difference.

When you are driving a company car then the road tax might not be as much of a concern to you, though the business may limit the models you can choose from based on this additional cost. However, you will then need to pay company car tax which is in part based on the CO2 emissions of a vehicle.

We recommend taking a look at this guide to company car tax and how it’s calculated to see what effect your fuel choice will have on this.

Is Diesel Right for You?

We know that choosing your next can be a challenge, as there are many factors to consider not just the fuel type which is why we’ve put together this guide to choosing your next company car. It gives general advice on the other things to consider.

When deciding if diesel is the best choice for you though we recommend taking into account all the pros and cons explored above and taking some time to do the maths on any costs like company car tax or parking permits that a diesel could have for you. We’ve also looked at the pros and cons of diesel compared with petrol, hybrid and fully electric here if you are weighing up another fuel option.

What are the Differences Between Diesel and Petrol? 

Though petrol and diesel vehicles both use a combustion engine to burn fossil fuel they operate in slightly different ways. 

For most drivers the main differences of note are:

  • Petrol is a cheaper fuel
  • Diesel is typically more fuel efficient 
  • Petrol has lower overall emissions but an equivalent diesel engine will emit less CO2

What Happens if You Put Petrol in a Diesel Car? 

If you incorrectly put petrol in your diesel vehicle then you should not drive it as the combustion process of petrol can cause major damage to your engine. Even turning the engine on will begin the internal combustion to provide power to the vehicle so we recommend not putting the keys in the ignition at all. 

You can move the vehicle into a safe location away from the pumps by putting it into neutral and pushing the vehicle to a parking space.

Petrol and diesel have different combustion processes and using petrol will damage the engine making the vehicle unusable until it's been repaired which can be an expensive process and won't be covered by most insurers or maintenance packages. 

What Does the 2030 Ban Mean for Diesel Cars?

From 2030 the sale of all new petrol, diesel and hybrid vehicles will be banned across the UK. This means that no new models can be sold after this date and we will likely see a decline in the diesel models on offer as we get closer to this date.

So far no measures have been suggested to restrict or reduce the sale of used diesel models so you will still be able to find diesel models on the market but they will not be brand new models. 

What Alternatives are There to Diesel Cars? 

Currently, you can find petrol, petrol and diesel hybrids and fully electric models if you don't want a pure diesel vehicle. We recommend taking a look at this guide to help you decide the best fuel type for your needs. You can also take a look at our collection of guides on the different fuel types available and the benefits and drawbacks for each of them to better understand the alternatives. 


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