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There are a lot of questions facing any new-car buyer, but one of the most fundamental is which fuel your car should run on.

Historically, the choice has predominately been between petrol and diesel, but electric and hybrid cars are increasing in popularity as the technology evolves.

When deciding which fuel – or power type – type is best for you, you shoulder consider several factors including:

• How much it will cost you in fuel or electricity
• Other running costs, including tax and depreciation
• The type of driving you do
• Environmental concerns
• How easily you can live with the car

Petrol

A petrol engine is the UK’s most popular choice, and there are plenty of good reasons why. For a start, petrol is a cheaper fuel than diesel, and petrol-engined cars tend to be cheaper to buy than the equivalent diesel model.

Those advantages have to be offset against the fact that petrol cars have higher fuel consumption (worse mpg) than diesels, so you’ll have to fill your tank more often. As such, petrol cars are at their most cost-effective for those that cover less miles.

In terms of environmental impact, petrol cars generally have lower nitrogen oxide (NOx) and particulate emissions than diesels but they do emit more CO2.

If you cover a low-to-medium annual mileage (around 6,000-7,000 miles) and you’re not convinced that a hybrid or electric car would suit you (or you can’t afford one), then a petrol car could be the right choice for you.

Find petrol cars on Auto Trader.

Diesel

Diesel cars generally give you better fuel economy (higher mpg), are cheaper to tax and produce lower CO2 emissions than equivalent petrol models.

They’ve developed something of a bad reputation for pollution, and do tend to produce more nitrogen oxide (NOx) and particulate emissions than petrol, but the latest diesels meet Euro 6 regulations, which set a strict limit on harmful exhaust emissions.

Diesel is slightly more expensive than petrol at the pumps, but the difference is such that if you cover a lot of miles a diesel is likely to cost you a lot less in fuel over time. Diesel cars are generally between 15 and 20% more fuel-efficient than the equivalent petrol model, so as your mileage rises, you reach the point where the amount you save in fuel bills makes up for any extra the car and fuel cost in the first place.

Modern diesel engines have a diesel particulate filter (DPF) to reduce emissions. These filters need regular long journeys at higher speeds to keep them working properly – if you generally only make short trips there is a risk that the DPF can clog up and fail.

Many diesel cars also need to be regularly topped up with AdBlue – a chemical that helps reduce the NOx emissions produced by the engines. If you cover a lot of miles you may have to top up with AdBlue yourself between services.

Overall, diesel cars still make sense for drivers who do a lot of miles, particularly on motorways. If you want to buy a diesel car, just make sure it meets the latest Euro 6 regulations.

Browse diesel cars on Auto Trader today.

Electric cars

Electric cars are increasingly popular thanks to their low running costs and environmentally friendly, zero-emissions status.

Technology has developed rapidly over the past few years, easing concerns over battery range. In fact, it has improved to the point where some electric cars are capable of 350 miles or so between charges. Around 150-250 miles is more common, however, so you still need to plan journeys more carefully than with a petrol or diesel car.

Running an electric car is often cheaper than petrol or diesel, because the cost to charge them is much lower than the cost of fuel for the same mileage. There are also major tax incentives, whether you are a private or business user.

Electric cars are generally more expensive to buy than a diesel or petrol equivalent, though, and the choice of brands and body styles available is limited. The number of options is increasing, however, with many car brands set to release new full-electric models over the coming months.

Your lifestyle and driving habits may well decide whether an electric car is right for you. While the number of public charging points has increased, finding one isn’t always easy, depending on where you are in the country. Home charging points are available, but not everyone is able to park directly outside their house or flat.

Electric cars are a great option for drivers who don’t often make long journeys and have easy access to charging points. As the technology and infrastructure for electric cars improves, they’ll become more and more viable.

Explore electric cars on Auto Trader, or browse our picks for the best electric cars of 2020.

Hybrids

Hybrids combine an electric motor (or motors) with a traditional internal combustion engine, but how they do so varies depending on the type of hybrid you’re driving.

Hybrids offer a solid balance between electric cars and traditional engines, often blending the benefits of both but sometimes bringing their limitations too. Which type of hybrid suits you will depend on your mileage, lifestyle and budget, among other factors.
Hybrid electric vehicles (HEV)
HEVs combine a petrol engine (there are no diesel HEVs on sale) and an electric motor. Switching between petrol and electric, or blending the two, is often done automatically, although many hybrids allow you to select different drive modes that prioritise efficiency or power.

Many HEVs have a limited electric-only range that will allow you to cover a short distance on electric power alone, at lower speeds. The electric motor is powered by a built-in generator that’s re-charged when you brake, so there’s no need to plug them in to charge the battery. HEVs need to be refuelled with petrol – thanks to the assistance provided by an electric motor they return better fuel economy than a petrol equivalent, as well as lower emissions.

The number of HEVs on sale is relatively small, as plug-in hybrid technology has become more prevalent, but they remain an effective compromise that will suit some buyers well.

Here's our picks for the best hybrids of 2020.
Plug-in hybrids (PHEVs)
Plug-in hybrids (PHEVs) sit somewhere between HEVs and pure electric cars. The battery in a PHEV has a much higher capacity, so it needs plugging into a charging point to fully charge – the on-board generator isn’t enough.

Generally, PHEVs drive on electric power first and swap to petrol (or, rarely, diesel), or a mix, once the full-electric range is used up. As such, they use significantly less fuel and have far lower emissions than HEVs.

While the official fuel economy and emissions figures mean there are currently big tax benefits for PHEVs compared with petrol or diesel cars it’s worth noting that real-world fuel economy will depend on how and where you drive and whether you keep the battery topped up. PHEVs are also more expensive than equivalent HEVs and petrol and diesel cars.

As a half-way house between internal combustion engines and full electric power, PHEVs are a fine option, but they do need to be regularly plugged in to get the best from them.

Pick up a PHEV here.
Mild hybrids (MHEVs)
Mild hybrids (MHEVs) have an electric starter-generator that stores the energy created when braking and then uses it to help out the engine and electrical system when accelerating, to increase efficiency.

It gives a small improvement in fuel economy and emissions over a conventional petrol or diesel engine, but not as much as an HEV or PHEV. Mild hybrid technology is becoming increasingly common in many petrol and diesel models, where it is included as standard.

MHEVs can’t run on electric power alone and most car brands don’t offer them as standalone models – it’s best to think of them simply as the next generation of petrol and diesel cars as we move towards increasing electrification.

Learn more about electric and hybrid cars.

Bi fuel

Bi fuel cars can run on two fuels. They have an internal combustion engine fuelled either by petrol or diesel, and another that runs on alternative fuel like LPG (liquefied petroleum gas, which is a mix of propane and butane), hydrogen or natural gas.

Find bi-fuel cars on Auto Trader.

Ultimately, no one fuel type will suit everyone, but if you take your time to work out the right one for you, you’ll have miles of happy – and cost-effective – motoring.
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