There’s been a big push towards electric vehicles recently, with the evolution of government grants and support schemes to assist drivers with making the transition to an EV. We know that an electric vehicle isn’t always the right choice at the minute for your business so we’ve also taken a look at the benefits and costs of diesel and petrol vehicles and hybrids.

What Is Diesel?

Diesel is one of the two main traditional fuels used with vehicles that have a combustion engine. 

It's been in and out of favour with the UK government over the years, with there initially being tax breaks for diesel vehicles due to lower CO2 emissions which were then reversed when the overall environmental impact was found to be worst. This does not mean you should never choose a diesel vehicle and in fact there are circumstances when you might find a diesel car will be better for particular drivers in your fleet. We've explored some of these benefits below.

What Are the Different Types of Diesel?

In the UK there are two types of diesel available. The main type available at the pumps is city or low sulphur diesel and the second is premium diesel. 

City / low sulphur diesel is the standard fuel type whereas premium diesel has a higher cetane rating which means it will burn more quickly and efficiently as well as containing cleaning agents and lubricant that reduce soot particles and oily residue build up in the engine and fuel system. It can be useful to fill up with premium diesel every tenth tank or so, to help reduce build up in the car's system but in general provided drivers are regularly running the vehicle at high speed over a significant distance then this should not be an issue. 

Benefits of Diesel Vehicles

There are a number of benefits that diesel engines can provide to your fleet.

Diesel has better fuel economy than petrol and does not require charging like an EV would, so if you need a vehicle for a driver who travels long distances regularly or has a high annual mileage. This would be especially beneficial to the business if you also run a fuel card scheme.

Typically, diesel engines are slightly larger and more powerful making them able to achieve greater torque, so they have better overtaking power and towing abilities. This makes them a good choice if you need a vehicle that is likely to be towing regularly.

A diesel car will also have lower CO2 emissions than petrol equivalents, however this is countered by higher levels of other emissions. We’ll explore these in further detail below

Considerations with a Diesel Vehicle

As we as the benefits listed above there are a few other aspects of a diesel vehicle that you’ll need to consider when deciding if it is the right choice for that particular vehicle need.

Diesel vehicles are typically a little more expensive than a petrol engine, which means that the cost of them will be higher, whether you are purchasing or leasing them.

Servicing and maintenance can also be a little higher when you opt for diesel as there are additional components like a diesel particulate filter (DPF) that other engine options do not have.

The diesel particular filter helps reduce emissions, but it also requires a particular type of driving in order to prevent it from becoming clogged. For example, if the vehicle will be used for constant, low-speed urban driving then the DPF will quickly become clogged and need replacing. On the flip side, if the vehicle is driven regularly on a higher speed road then it is less likely to become blocked.

Another consideration that you will want to make is whether your business, or the driver’s home address, is located in a city that has, or is introducing, a low emission or clean air zone. We recommend checking your business address and the driver’s address to ensure that these aren’t in or about to be in one of these areas where diesel cars are more heavily penalised, by higher tariffs.

If the intended driver lives in an area with a residential parking permit scheme then they will also want to check that their local authority isn’t applying a diesel surcharge, as some apply a higher rate for diesel vehicles.

Will Diesel Cars be Banned?

Yes, they will. As part of the government's commitment to having all new vehicles being sold as zero emission ones the sale of new diesel vehicles will be stopped from 2030.

However, the sale of used diesel vehicles will still be allowed after this date until they gradually phase out as fleets and private vehicles are updated to newer models.

Deciding If Diesel is Right for Your Business

When deciding if diesel is the right choice for your business or a particular driver you will need to take into account all of the above pros and cons of diesel engines and the impact they will have.

We recommend considering the fuel type you are looking at for each vehicle you select for your fleet, as every driver’s needs will be different and if it is a vehicle to be used by multiple people then the requirements will also be different.

We’ve compared the pros and cons of diesel, petrol, fully electric and hybrid vehicles here so you and your drivers can compare them to decide which is the right choice for you.


Diesel Vehicles and the Environment

One of the biggest concerns that drivers and businesses looking at expanding their fleet when considering a diesel engine is the environmental impact they have.

Although modern diesel engines are much cleaner than the original models the emissions they are still considered to be the most pollutant of engine options available.

Diesel cars produce and emit less CO2 than a petrol engine however they do emit more of other pollutants like nitrogen oxide. These pollutants are why modern diesel vehicles are fitted with a diesel particulate filter (DPF) which cuts down on the emissions the vehicle produces. As mentioned above it’s important to bear in mind the conditions needed to prevent the filter from being clogged.

Additionally, most diesel vehicles are also fitted with technology that converts most of the nitrogen oxide into nitrogen and oxygen before reaching the exhaust and these are both harmless to the environment.

Car manufacturers are working hard to continue to reduce the environmental impact of their business as well as that of their vehicles and diesel cars are cleaner than ever before with many now complying with the Euro 6 emission standards.

Euro 6

The Euro 6 emission standards were introduced in 2015, following the previous five emission standards, and are designed to place more stringent restrictions on vehicles to reduce their emissions. Many emission zones, congestion charges and other countries if you’re travelling in your vehicle have restrictions or increased charges for vehicles that are not compliant.

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


Another standard of testing that is used to measure a vehicle’s emission levels in the UK is the Real Driving Emission (RDE) test.

In RDE testing the vehicle is not tested in laboratory conditions but rather under real world driving conditions in order to provide users with a more accurate measurement of a vehicle’s emissions.

These tests were introduced in September of 2017 and since 2019 it has been mandatory for all new vehicles to be sold in the UK to go through these.

There are two stages of testing for RDE testing and the first of these, RDE1, allows a car to emit 2.1 times the amount of nitrogen oxide that is allowed during laboratory testing conditions.

RDE2, which is the standard that all new vehicles must now be compliant with, allows for them to emit just 1.5 times the amount of nitrogen oxide.

If you want to find out more about the impact of CO2 and why it’s important that you consider this as well as the other emissions of a vehicle then take a look at this guide.

Diesel Vehicles and Tax

The amount of road tax you are required to pay on a vehicle is dependent on their emissions and so diesel models tend to be slightly more expensive. This is especially true if they are not RDE2 compliant.

If you have any leased vehicles in your fleet they you will not need to be as concerned about the road tax on these as the tax is paid by the lease funder, though they may invoice you the difference if there is a rise in road tax from the initial registration.

If the vehicles are owned by the business then you will want to take into consideration the road tax implications of choosing a particular fuel and engine type and keep in mind that this will be an annual cost for the vehicle when looking at the budget implications.

With a vehicle that is being driven by one of your employees as a company car then it would also be wise to consider the company car tax implications. Company car tax is in part based on the CO2 emissions of a vehicle, and so if other factors also line up, then you might opt for a petrol rather than a diesel engine because of this.


Are Diesel Cars Better Than Petrol?

This depends on what you are looking for in a car. If you want a cheaper initial purchase price or monthly lease then you might find better deals on a petrol engine. If you want better fuel economy then you might be better looking at a diesel.

Take a look at this guide if you want to find out more about how the two compare.

Are Diesel Cars More Expensive Than Other Fuels?

Diesel cars tend to be more expensive to purchase than an equivalent petrol model due to the more expensive and additional parts like the diesel particular filter they need. However, hybrid and EV versions will be more expensive than diesel models as they have more expensive production costs.

If your business is going to lease a vehicle then then higher purchase prices will usually be reflected in higher monthly payment prices for the lease agreement so no matter how you fund the vehicle you will tend to find that the cheapest to most expensive will be petrol, diesel, hybrid then EV. 

However, when you take into account running costs a diesel can often work out cheaper over it's lifetime than other options as it can get great fuel economy compared with petrol cars, cheaper maintenance and servicing when compared to hybrids and EVs. It's important when you're looking at the cost of a a vehicle that you take into account the cost of running it, maintenance 

For more information on fuel types, fuel cards, leasing and fleet management head back to our business guides homepage or get in touch with us here


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