Should I buy a diesel car? The future of diesel cars in UK

Diesel cars might be demonised, but can still be a good option for some drivers. Read on to understand when it makes sense to get a diesel

BuyaCar team
Jun 8, 2022

Diesel cars are no longer the de facto choice for drivers on the lookout for cheap running costs. Diesel engines are still more economical than equivalent petrol engines in terms of fuel consumption, but that is where the list of advantages comes to an end.

While diesel models used to be hugely popular - partly thanks to their lower-than-petrol CO2 emissions and consequently cheaper road tax - they have slowly been pushed out of fashion by a succession of tax increases, parking surcharges and city centre low-emission zones that penalise older diesels. Another factor that might put off some buyers is the announcement that sales of brand new petrol and diesel cars will be banned in 2030.

A succession of negative headlines surrounding diesel car emissions has seen the number of new models sold in the UK shrink substantially since news of the 'Dieselgate' scandal first emerged in 2015. This downward spiral has been exacerbated by the introduction of strict government measures designed to limit the amount of exhaust emissions polluting the air in the UK's city centres.

Despite this, diesel cars can still be the best option for some drivers - especially those who do lots of long journeys on higher speed roads - like dual carriageways and motorways. So read on to get to grips with whether a diesel car could work for you.

Diesel cars in London

London's Ultra-low Emission Zone (ULEZ) first began operating in April 2019 and imposes a compulsory charge of £12.50 for the majority of pre-2015 diesel vehicles entering the city with a view to deterring their use and reducing air pollution. The area affected grew dramatically in October 2021, so this now applies to the vast majority of London and many of its suburbs.

The capital's ULEZ scheme has been followed by a succession of new clean air zones (CAZ) being set up in city centres around the country, which will also mainly target diesel cars, as these can produce high levels of certain exhaust emissions.

With this in mind, you'd be forgiven for steering clear of diesel altogether when you choose your next car. Many drivers are doing just that and new diesel car sales have fallen dramatically over the past few years.

To counter this latest hurdle, the latest diesel cars have been developed to produce fewer emissions and meet the 'Euro 6' emissions standard that the ULEZ and other clean air zones require, so the risk of being caught out by additional fees for driving a diesel car have been notably reduced for now. Virtually every brand new car sold since September 2015 has had to comply with the Euro 6 limits.

Should I buy a diesel car?

Diesel taxes and surcharges have cut demand for diesel cars, but they remain cheaper to run than petrol cars for most high-mileage drivers thanks to excellent fuel economy.

Diesel pulling power is also ideal for large vehicles and towing, with most diesel engines offering lots of muscle from low engine speeds. Modern diesels meeting Euro 6 emission limits are exempt from ULEZ and CAZ charges, so if you are in the market for a larger vehicle like an SUV or pick-up, a diesel engine is often the best way to go.

It's also important to note that it's not just diesel cars that have their doomsday clocks counting down. Petrol cars will also begin to meet tougher and tougher restrictions as the electric car market progresses, so if you are intent on sticking with fossil fuels for the time being, and provided you aren't intending to make regular trips into major city centres, a diesel-powered car is still capable of making you some pretty substantial savings.

Choose petrol for...

Driving less than 12,000 miles per year
Small- or medium-size vehicles
Mainly city driving (especially London)
Lower air pollution impact

Consider a diesel for...

High annual mileages
Big vehicles, including SUVs
Larger company cars
Towing heavy loads

Diesel cars that avoid emissions charges

You can reduce the risk of being hit with inner-city diesel charges by buying a newer diesel car that complies with the latest emissions regulations, called Euro 6. These vehicles are not subject to charges in London's ultra-low emission zone (ULEZ), nor the clean-air zone which has been in place in Birmingham since 1 June 2021. Every car registered since September 2015 is required to meet the Euro 6 standard, although there are several examples of diesel cars that met this standard prior to it becoming a requirement. All diesel Mazda CX-5 models have met the standard since 2012 for example, so they should be exempt from inner-city charges.

Cars that meet future emissions regulations (called RDE2 or Real Driving Emissions Step 2, or Euro 6d) will be exempt from the recent road tax increases. The first diesel models that meet this standard are already on sale, and include some versions of the latest Mercedes A-Class, the BMW 2 Series Active Tourer and BMW 2 Series Gran Tourer, the latest Ford Kuga and the Volkswagen Golf.

Further into the future, London plans to introduce a zero-emission zone in 2025. This is expected to ban petrol and diesel cars from the very centre of the city, and gradually expand until it covers all of the capital in 2050. Oxford plans a zero-emission zone too, which would ban diesel and petrol cars from parts of the city centre.

Diesel cars: new or used?

All brand new cars comply with the latest Euro 6 regulations. As mentioned above, there are no plans to charge owners of these vehicles for driving in city centres in the next few years.

Diesel cars that only meet the previous, Euro 5 emissions standard (or even earlier standards), are subject to emissions charges in London. Other cities may also charge these cars for driving within central clean air zones, too.

When you're buying a used car, it's worth checking which standard it meets. Some manufacturers only complied at the last minute, selling Euro 5 cars right up to September 2015, when Euro 6 became mandatory.

Like many retailers, BuyaCar often publishes the Euro standard of each used car in the technical information that accompanies many listings. It's worth asking for this to be double-checked when you come to make a purchase to ensure that your car is compliant if this is something that is important to you.

Diesel cars: depreciation

Diesel car values began falling faster than those of petrol cars in 2017, according to the car valuation firm cap hpi. That trend appears to be accelerating, with some nearly new diesel cars selling for less than their petrol equivalents, despite costing more when new.

Many think that a catastrophic plunge in values is unlikely. As diesel cars become cheaper, they will offer very good value for money, even with extra taxes and charges, which is likely to lure some buyers back. Cap hpi also says that larger vehicles should hold their value better in diesel form, as petrol versions can be extremely expensive to run.

To protect yourself against the uncertainty, taking out PCP finance will mean that you don’t have to shoulder the risk of the car plummeting in value, should demand for diesels reduce.

This is because PCP finance gives you the choice of keeping your car at the end of the contract by paying a pre-agreed lump sum, or handing it back with nothing more to pay (provided you've kept it in good condition and not covered more miles than agreed) - even if it has lost much more value than initially expected.

When will diesel cars be banned UK: the future of diesel cars

The government has announced that the sale of new petrol and diesel cars will be banned by 2030, along with most hybrid cars that use existing technology.

Although it sounds like a drastic measure, the policy may not actually have a dramatic impact. That's because the motor industry expects that the majority of cars sold will either be more advanced hybrid cars that are exempt from the ban, electric, or even hydrogen-powered by 2030.

Even if your petrol or diesel car is still running in 2030, there are no plans to ban it from the roads entirely, as second-hand sales are expected to be unaffected. However, London's mayor has proposed banning them from driving in the capital, starting with the centre in 2025. Other cities may follow suit.

Petrol or electric cars: best for low-mileage drivers

If you drive less than 12,000 miles per year, then a petrol car is likely to be the best value option, particularly if you’re looking for a small- or medium-size car.

That’s because petrol vehicles generally have a lower price than diesel cars, and lose value at a similar rate, which makes the cost of buying or financing them cheaper.

In general, you’ll typically have to drive more than 12,000 miles per year in a typical family hatchback for the lower fuel costs of a diesel car to outweigh the higher purchase price. That’s without factoring in any additional diesel surcharges, which will skew the balance even further in favour of petrol.

It’s also worth considering an electric car. Most of the latest models, including the Volkswagen ID.3, Peugeot e-208 and Jaguar I-Pace, can all achieve upwards of 200 miles on a single charge. Electricity should also be cheaper than petrol, which could dramatically cut your running costs.

Petrol engines: best in small or medium-sized vehicles

Advancements in engine technology have brought petrol engines closer to the fuel economy figures of diesel motors, particularly in smaller and lighter cars.

That means that any fuel savings you'll make by choosing a diesel supermini or family car are likely to be small, and may not make up for the higher purchase price that diesel cars typically have.

Before you make your decision, it is worth checking the real-world fuel economy of a new car. Some of the most advanced petrol and diesel engines are extremely good at returning high mpg figures during the official European fuel economy test, carried out in a laboratory, but deliver much lower figures in normal driving.

Petrol or electric cars: best for city driving

Recent announcements of clean air zones have confirmed that diesel car drivers will face hefty charges or outright bans in some city centres, including London, Birmingham and Glasgow. It makes the choice of petrol a no-brainer for drivers who rarely stray out of town - particularly if you’re looking for a cheap car that’s a few years old or more, which is unlikely to meet the latest emissions regulations.

Newer diesels, which meet the Euro 6 standard, should initially be exempt from clean air zone charges because they are less polluting, but they still don't make the best city cars.

Petrol or electric vehicles have always been best for short journeys, such as shopping trips or the school run because they don’t need exhaust filters. Modern diesel cars have these filters to trap harmful soot particles, which can become clogged unless you regularly make long journeys on faster roads, when hotter exhaust gases are able to burn off the particles are produced.

City drivers will also benefit the most from hybrid cars, which can recover energy that’s normally wasted during stop-start driving. In these situations, fuel economy is considerably better than in conventional petrol vehicles.

Petrol or electric cars: best for reducing air pollution

Microscopic soot fragments from car exhausts - known as particulates - and nitrogen oxides are known to contribute to respiratory diseases and are responsible for tens of thousands of early deaths in Britain each year. Diesel cars emit far more of these pollutants than petrol vehicles.

Euro 6 emissions regulations were meant to bring diesel emissions in line with petrol cars, but real-world testing suggests that many cars don’t come close to the required standard when they are driven on the road.

These vehicles still remain legal because they pass the official emissions test, which is carried out in a laboratory, but if the pollution produced by your car is a big concern - particularly if you drive in built-up areas, where it's most likely to affect people - then until recently, a non-diesel car has been best.

This is likely to change in coming years, as new cars will have to pass a much tougher test, carried out on public roads, known as Euro 6d. An interim test, which isn't quite as tough, has been introduced to give car makers time to re-engineer their cars and it is already having an effect. Research from Germany suggests that many of the very latest diesel cars almost match petrol versions for harmful nitrogen oxide emissions - and a few are cleaner.

Diesel cars: best for long-distance drivers

If you travel more than 12,000-15,000 miles a year, then the additional cost of a diesel car may be outweighed by the savings you make from its superior fuel economy. This is more likely to be the case if you’re buying a larger car because petrol engines require far more fuel to get heavier vehicles moving.

Whether it's cost-effective for you will depend on the mileage that you do, as well as the specific price and fuel economy of the cars that you are considering.

The air pollution impact of diesel cars is also less when they are driven outside of built-up areas, as the harmful emissions can disperse with far less impact on health.

If your long-distance driving takes you into towns and cities, there is a risk that paying to enter clean air zones will cancel out any fuel savings. To avoid that possibility, then you are best off looking at a newer diesel car that meets the Euro 6 emissions regulations. These vehicles won’t be affected by London emissions charges, and are expected to avoid other city emissions charges.

Diesel engines: better for larger cars

Diesel engines are more efficient than petrol models. In heavy cars, which need more energy to get moving, that difference adds up to greater savings.

The way that diesel engines work also makes them more suited to larger cars: you don't need to press the accelerator hard or work the engine quite as much to feel a burst of power. Even a medium-size diesel engine is powerful enough to get a big and heavy SUV moving quickly, with little apparent effort.

In contrast, you need to work many petrol cars hard to get that same surge of power, reducing fuel economy even further. It’s not uncommon for an SUV with a diesel engine to offer around twice the fuel economy of the petrol version of the same vehicle.

That makes diesel the fuel of choice for people carriers, SUVs and pick-up trucks. Some hybrid SUVs combine a petrol engine with an electric motor, which offers impressive fuel economy on shorter journeys, but they aren't ideal for everyone because their efficiency quickly drops on longer trips, and the cars are far more expensive to buy than their petrol or diesel counterparts.

Diesel engines: good for large company cars

The new car tax system has reduced much of the advantage that diesel vehicles used to have because, unlike the previous system, it’s no longer solely based on carbon dioxide emissions (CO2). This reduces the incentive for drivers to buy diesel-powered cars.

However, the current company car tax regime is still linked to CO2, so you may make savings with a diesel vehicle.

It will have to be efficient, though, because rates for diesel cars are 4% higher than petrol vehicles. This makes small petrol cars cheaper for business users. But large diesel-powered cars, including SUVs, are so much more fuel-efficient than petrol versions, that they tend to attract cheaper rates of company car tax.

As business users tend to run brand new cars, vehicles should comply with the current Euro 6 emissions regulations, so won't be affected by the London clean air zone.

Diesel cars: better for towing

Just as diesels are best at getting heavy vehicles moving, they are also the engine of choice for towing. Their substantial low-engine-speed pulling power - known as torque - is much more effective at hauling a heavy caravan or trailer away from a standstill or up a hill.

In smaller cars, petrol engines may simply not be up to the job and not be able to cope with towing loads up steep hills. Even if they can pull away, the fuel bills may give you nightmares compared with a diesel alternative.


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