Should I buy a diesel car?

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

BuyaCar team
Nov 22, 2017

Taxes for many diesel drivers went up in this month's Budget, adding to a series of measures that penalise owners of diesel cars. These include parking surcharges, toxicity charges for driving in some city centres, and even proposals to ban certain diesel cars from some roads.

So it's not surprising that sales of new diesel cars plunged by 30% last month and that rising numbers of owners are turning to diesel scrappage schemes, which offer a significant discount on a new car if they ditch their old vehicle. Three in five diesel drivers plan to change their car for a petrol, hybrid or electric model, according to a recent BuyaCar survey.

It's true that large numbers of drivers are better off buying a non-diesel car, avoiding any worry and uncertainty - as well as extra costs. But behind the headlines, diesel vehicles can be a better option for many drivers - particularly for those after a large sport utility vehicle (SUV) or people carrier.

The tax rises announced in the Budget were lighter than many expected, and will only affect company car drivers or anyone buying a brand new car from next April.

And as buyers avoid the cars, prices are dropping, which makes diesel cars more affordable. Some nearly new diesel cars are now available with more than 25% off their new price, making them cheaper than the equivalent petrol car. Buying on finance can protect against an unexpectedly high loss of value.

Read on to find out whether diesel is right for you. Scroll further down the page for our diesel car buying advice, including how to avoid future charges when buying a used car.


Choosing a petrol or diesel car

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Diesel car buying advice    

Keep scrolling down for our detailed advice on buying petrol and diesel cars to suit your circumstances. You'll also find extra help on buying a diesel car. Read on for all the details or jump to our brief guides on:


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. In London, these vehicles will not be subject to any planned emissions charges. Current indications are that they will also be exempt from charges in up to 27 other cities which could set up clean air zones. Oxford plans a zero emissions zone from 2020, which would ban diesel and petrol cars from parts of the city centre.

Every car registered since September 2015 is required to meet the Euro 6 standard, and many complied earlier (see below).

Recently announced increases to road tax for brand new cars and company car tax will affect all current diesels, but models built in the coming years will be exempt if they meet a stricter emissions standard (called real Driving Emissions Step 2). There is no indication of when these vehicles will go on sale as yet.  

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.

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Differences when buying a new or used diesel car

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

Diesel cars that only meet the previous, Euro 5 emissions standard (or even earlier standards), will be subject to emissions charges in London from 2019. In the same 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. But others sold Euro 6 compliant cars well in advance: all diesel Mazda CX-5 models have met the standard since 2012, for example, and so should be exempt from inner city charges, based on current information.

Like many retailers, BuyaCar publishes the Euro standard of each used car in the technical information that accompanies each listing (see below). If it's a key concern, you should ask for this to be double-checked.
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Protect yourself against a drop in value of diesel cars

Diesel car values began falling faster than those of petrol cars earlier this year, according to the car valuation firm cap hpi. That trend appears to accelerate, with some nearly-new diesel cars selling for less than their petrol equivalents, despite costing more as new cars.

Prices are unlikely to recover, given the indication that many drivers are abandoning diesel. However, 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 leasing a diesel car or 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.

Vehicle leasing is a long-term car rental agreement with fixed monthly payments. As you never own the car and hand it back at the end, you’re not responsible if it’s worth less than expected on the used market.

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. If it has dropped substantially in value, then you are unlikely to be able to trade it in for a different car at a large discount, which could otherwise be an option.
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2040 diesel and petrol ban

The government has announced that the sale of new petrol and diesel cars will be banned by 2040.

Although it sounds like a drastic measure, the policy may not actually have a dramatic impact. That's because many hybrid cars (which use a battery and motor alongside a petrol or diesel car) will be able to remain on sale under the current plans.

The motor industry expects that a majority of cars sold will be electric, hybrid, or even hydrogen-powered in 23 years'-time, and that conventional cars will be dying out in any case.

Even if your petrol or diesel car is still on running in 2040, there are no plans to ban it from the roads entirely, although London's Mayor has proposed banning them from driving in the capital, starting with the centre in 2025. Other cities may follow suit.
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Why petrol or electric cars are best for low mileage 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.
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Why petrol engines are best in small or medium-size 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.
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Why petrol or electric cars are best for city driving


The possibility of clean air zones, which impose charges on diesel cars being driven in certain cities, 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 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.
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Why petrol or electric cars are best for reducing air pollution

There is increasing evidence that microscopic soot fragments from car exhausts - known as particulates - and nitrogen oxides 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.

The latest 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 a non-diesel car is best.
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Why diesel cars are 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.
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Why diesel engines are 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.
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Why diesel engines are 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 3% higher than petrol vehicles and this will rise to 4% from April 2018. 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.
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Why diesel cars are 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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Confirmed diesel emissions charges


Low emissions zone

Location Central London
Start date T-Charge: October 23, 2017
ULEZ: April 8,2019
Cars affected T-Charge Pre-Euro 4 cars (most vehicles registered before 2006)
ULEZ Pre-Euro 6 diesel cars (most vehicles registered before Sept 2015) and pre-Euro 4 petrol cas
Cost T-Charge £10 per day ULEZ: £12.50 per day

Parking permit charges

Location London councils, including Islington, Camden, Merton and Hammersmith & Fulham
Start date In place now
Cars affected All diesel cars
Cost Surcharge ranges from £20 to £100 a year

On-street parking surcharge

Location Marylebone, central London
Start date In place now
Cars affected All diesel cars
Cost Diesel cars pay 50% more for parking: £7.20 per hour, compared with £4.90 for petrol cars
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Proposed diesel emissions charges

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Inner city clean air zones

Location Up to 27 towns and cities outside London, likely to start with Leeds, Nottingham, Birmingham, Derby and Southampton.
Start date Expected to be 2019
Cars affected Unconfirmed. Likely to be focused on older diesel cars
Cost Unknown. Government has dismissed suggestions that it could be up to £20 a day
Likelihood of being introduced 70%

Oxford zero emissions zone

Start date Proposed for 2020
Cars affected Petrol and electric cars
Cost Outright ban on affected vehicles - no charge
Likelihood of being introduced 60%

Ban on new petrol and diesel cars in London

Start date Proposed for 2040
Cars affected All new cars bought after 2040
Cost Unknown
Likelihood of being introduced 75%
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