Should I buy a diesel car? Here’s everything to consider

Diesel cars were once a very popular choice for drivers. Road tax has long been structured around a vehicle’s CO2 emissions, and diesel cars greatly benefited from this, incentivising many people to switch to a diesel engine to help curb emissions of harmful greenhouse gases.

But over the last decade, the future of diesel cars has been put into question. This is a result of stricter emissions testing, higher tax rates, initiatives such as the Ultra Low Emission Zones (ULEZ) and Clean Air Zones (CAZ), and the ban on new purely petrol and diesel cars due to come into effect from 2030, with hybrids allowed until 2035.

For many people, diesel cars still offer a more practical and economical solution compared to petrol cars, particularly as newer Euro 6-compliant diesels enter the market. However, these recent pain points along with the upcoming 2030 ban on new diesel cars have begun to make people question if buying a diesel car is worth it.

In this guide, we’ll take a closer look at the benefits and drawbacks of diesel cars to help you decide if buying a diesel car is right for you.

Reasons why you should get a diesel car

Better fuel efficiency

Diesel fuel contains more energy than petrol when comparing the same volumes. On average, diesel engines can return between 50 and 65mpg, compared to petrol engines which typically average 35 to 45mpg, with the biggest gap on longer, steady-speed motorway journeys. At the pumps, diesel currently costs around 15p more per litre than petrol on average, so it's worth weighing that against your likely mpg savings. If you regularly drive long distances, then a diesel car could save you money, despite the difference in fuel costs.

Durability and endurance

Diesel engines are typically built to be more robust to handle the high compression force of the ignition cycle. Because of this, diesel engines are renowned for being incredibly reliable.

The composition of diesel also helps to lubricate the engine and its moving parts when it’s in use which can further improve its longevity. On the other hand, petrol is a solvent. Over time, this increases wear within the petrol engine which can lead to higher maintenance costs.

Higher used values

Generally speaking, when it comes to used cars, newer large diesel cars hold their value better than petrol alternatives. As we’ve discussed, diesel cars are renowned for their robustness and this is often reflected in their price, even on the second-hand market.

That being said, with the 2030 ban on new purely petrol and diesel cars edging closer, resale values for older, non-compliant diesels have already begun to soften faster than for newer, Euro 6-compliant models, so it can be hard to predict if this will always be the case.

Towing capabilities

Diesel engines have a high compression ratio, which results in greater torque. Put simply, the more torque your engine has, the greater amount of pulling power it can produce.

This torque makes diesel cars more suited for tasks that involve towing heavy loads such as a caravan, horsebox or trailer.

Reasons why you shouldn’t get a diesel car

Short journeys are less efficient and can harm the engine over time

Diesel engines work best when fully warm and short journeys don’t give the vehicle enough time to warm up to the optimal level. Driving lots of short journeys in a diesel car puts additional strain on the engine, which can lead to more costly repairs over time.

Petrol and electric cars are much more suited for shorter commutes around cities and towns. Whereas diesel cars are more suited for long-distance and motorway driving.

Newer models can be more expensive to buy

Newer diesel models can be more expensive to buy due to advancements in technology that strive to make them more eco-friendly. If you regularly make long journeys, taking into account that better fuel economy can sometimes outweigh the initial price tag.

If purchasing a brand-new diesel car is out of your price range, you could consider purchasing a used diesel car. You can often find high-spec models at a lower purchase price. You could also consider using car finance to spread the cost rather than buying the vehicle outright.

Subject to CAZ and ULEZ charges

Some diesels are subject to Ultra-Low Emissions Zone (ULEZ) or Clean Air Zones (CAZ) charges. If you live or commute within these zones, then this is something you should consider.

For ULEZ, Non-compliant vehicles are subject to a daily charge of £12.50 in all London boroughs. Most Clean Air Zones outside London target commercial vehicles like taxis, vans and HGVs rather than private cars, though Birmingham and Bristol are exceptions, charging non-compliant private cars £8 and £9 a day respectively.

A diesel vehicle must comply with Euro 6 standards to be exempt from these charges. This is usually most vehicles registered with the DVLA after September 2015. However, Euro 6 standard diesel cars are usually more expensive. Therefore, you should weigh up the savings you would make on fuel and running costs with these potential CAZ and ULEZ charges.

Older diesels can be more polluting

Although diesel cars emit fewer regulated pollutants, they do emit more noxious gases and particulates. This is particularly prevalent for older diesel cars which have been deemed as a major contributing factor in air pollution in the UK.

Newer Euro 6-compliant diesel cars have improved technology to combat this. However, this usually comes with a higher price tag.

Legislative changes

A ban on the sale of new purely petrol and diesel cars is set to come into effect from 2030, with full hybrids allowed to continue being sold until 2035. From 2035, every new car sold in the UK will need to be zero-emission at the tailpipe. This won’t apply to existing vehicles already on the road, but it is unclear how it will affect the second-hand market in the years ahead.

Diesels will remain on the road for several years after this ban. However, like any car, they will eventually require maintenance and replacement parts. In the future, sourcing these parts may become harder and more expensive as diesel cars are phased out.

The future of diesel cars

The government has confirmed that the sale of new cars powered solely by petrol or diesel engines will be banned from 2030. Full hybrid models will still be allowed to be sold new until 2035, at which point every new car sold in the UK must be fully zero-emission. This only applies to new vehicles, so the sale of second-hand petrol, diesel and hybrid cars won’t be affected.

You will still be able to drive, buy and sell your existing petrol or diesel car after 2030. If you want to buy new, though, your only non-electric option will be a hybrid, until that route also closes in 2035. It is unclear what effect this will have on the second-hand market, but demand for well-maintained used diesels is likely to remain strong as the pool of new alternatives narrows.

Whilst buying a new petrol and diesel car will still appeal to many, others are looking at their options when it comes to fully electric cars.

Is it worth buying a second-hand diesel car?

Buying a used diesel car can offer very good value for money compared to buying a brand-new model. Despite the decrease in new diesel car sales in recent years, there has been a shift in demand towards the used diesel car market.

Diesel cars are renowned for their longer service life, which can make a second-hand diesel a more reliable option than petrol. Of course, this will depend on the age of the vehicle and how it has been maintained.