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

Diesel might be demonised, but it can still be a good option - see when's best to buy a diesel car and what the future holds

BuyaCar team
Sep 22, 2020

The once mighty diesel car has slowly and methodically been pushed out of fashion by a succession of tax increases and parking surcharges. The announcement of a future sales ban well and truly put the frugal fuel savers on the ropes, now low emission zones have come in to deal the knock-out blow.

London's ultra low emission zone (ULEZ) first began operating in April 2019 and imposed a compulsory charge of £12.50 for the majority of diesel vehicles entering the city.

The capital's charging scheme is set to be followed by more clean air zones (CAZ) being set up in city centres around the country in early-2021, which will also mainly target diesel cars producing dangerously high levels of 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: new diesel car sales were down by a quarter in 2018 (it was a similar story in 2019 and so far in 2020), and a recent BuyaCar survey found that three in five diesel drivers planned to change their car for a petrol, hybrid or electric model.

But while many will be better off buying a non-diesel car, diesel engines still have a place in the market thanks to their fuel efficiency and power, which are ideal for high-mileage drivers and those looking for an SUV. As demand for these engines drops, you may get a bargain too, while taking out a finance deal can protect against an unexpected loss of value.

To counter this latest hurdle, new diesel cars have been developed to produce fewer emissions and meet the Euro 6 emission standard that the ULEZ and CAZ require, so the risk of being caught out by additional fees for driving a diesel car have been dramatically 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. Modern diesels meeting Euro 6 emission limits are exempt from ULEZ or 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 really 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 a year
Small- or medium-size vehicles
Mainly city driving (especially London)
Lower air pollution impact

Consider a diesel for...

Large annual mileages
Big vehicles, including SUVs
Larger company cars

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 upcoming clean-air zone in Birmingham. 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, based on current information.

Cars that meet future emissions regulations (called 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 Mercedes A-Class.

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 emissions zone from 2020, 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. From the end of this year, other cities may also charge these cars for driving within central clean air zones.

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.

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 value-for-money, even with extra taxes and charges, which is likely to lure buyers back. Cap hpi also says that larger vehicles should hold their value better, as petrol versions can be extremely expensive to run.

To protect yourself against the uncertainty, then 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.

PCP (Personal Contract Purchase) agreements give you the choice of keeping your car at the end by paying a pre-agreed lump sum, or handing it back with nothing more to pay - even if it has lost much more value than expected.

The future of diesel cars: 2040 diesel and petrol ban

The government has announced that the sale of new petrol and diesel cars will be banned by 2040, 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 a majority of cars sold will either be more advanced hybrid cars that are exempt from the ban; electric; or even hydrogen-powered in 22 years-time.

Even if your petrol or diesel car is still running in 2040, 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 cars: best for low-milage drivers

If you drive less than 12,000 miles a 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 a year in a 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 Renault Zoe, Nissan Leaf and Hyundai Ioniq can manage a 100-mile-a day commute if you can charge them fully overnight. That can dramatically cut your running costs.

Petrol engines: best in small or medium-sized vehicles

Advances 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.

This is particularly true of small turbocharged engines. These need revving to get the best performance out of them, which increases fuel consumption.

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 rarely stray out of town - particularly if you’re looking for a car that’s a few years old, 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. The filters can become clogged unless you regularly make long journeys on faster roads, when hotter exhaust gases that 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 conventional 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 carmakers 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 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 the forthcoming 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 rev the engine to feel a burst of power. Even a medium-size diesel engine is powerful enough to get a big and heavy sport utility vehicle (SUV) moving quickly, with little apparent effort.

In contrast, you need to rev many petrol cars 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 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 expensive.

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 buy brand new cars, vehicles should comply with the current Euro 6 emissions regulations, so they aren’t affected by the London clean air zone.

Diesel cars: better for towing

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

In smaller cars, petrol engines may simply not be up to the job and stall on steep hills. Even if they can pull away, the fuel bills will give you nightmares.


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