Diesel, Petrol, Electric & Hybrids: The Pros & Cons

A few decades ago, buying a car was as simple as looking at the price tag: if it was in your budget, it was the right choice.

But cars have evolved since then. What’s cheapest is no longer the only priority. The types of fuel our vehicles use is now also a significant factor in the choices we make; not only is it getting more expensive, but reducing emissions is now a bigger priority than ever before.

To help you better understand what kind of car you should opt for, we explain everything you need to know about diesel, petrol, electric cars and hybrids.

Diesel vs petrol cars

What’s the difference between petrol and diesel?

Petrol is a liquid fuel made by distilling petroleum. It’s used in traditional combustion engines, where the fuel is ignited (combusted) with a spark. Petroleum is produced from fossil fuels like crude oil, hydrocarbons, coal and natural gas.

Diesel, on the other hand, is a manufactured liquid fuel that can be used to power a diesel engine. Diesel engines use air compression to ignite the fuel rather than a spark and have a higher thermodynamic efficiency — and therefore fuel efficiency — than petrol engines.

Why is diesel more expensive than petrol?

In the UK, diesel is typically more expensive than petrol for a couple of reasons:

  1. It’s getting more expensive to make —While diesel used to be cheaper to produce than petrol, modern laws require a more complex refining process to make it as low in sulphur as possible.
  1. It’s designed for commercial users — Though more people drive unleaded vehicles than diesel vehicles, there’s more diesel sold in the UK than petrol. This is because there is a high volume of commercial vehicles in the UK using diesel power. Business motorists are less likely to shop around for better forecourt prices since they’ll be able to claim the fuel back on their expenses. That means retailers can afford to increase their prices and make a bigger profit.

Is diesel better than petrol?

Petrol and diesel engines both have their pros and cons, so it’s not easy to say which is ‘better’. It depends on what you prioritise; while diesel cars are more fuel-efficient, petrol cars produce fewer emissions and are typically cheaper to buy.

Not too long ago, diesels were said to be more environmentally friendly than petrol cars. There were even tax breaks to encourage more people to drive them.

But more recently, diesel car taxes have been hiked up and sales have fallen because that view has changed. It’s now thought that petrol engines are actually the cleaner option of the two.

Yet while petrol might be a little kinder to the environment than diesel, they both pale in comparison to newer innovations in green travel: hybrid and electric cars.

Electric and hybrid vehicles

What is an electric car?

An electric car, or ‘electric vehicle’ (EV), is a car that is powered by a built-in battery instead of the traditional combustion engine used in petrol and diesel cars.

EVs are fitted with a battery pack connected to an electric motor. This battery pack can be charged using a specially made charging cable, either at home or at one of the 17,000 designated charge points in the UK.

Best of all, electric cars don’t need an exhaust pipe. That means zero emissions on the road — perfect for anyone who wants to reduce their carbon footprint.

What’s the difference between an electric car and a hybrid?

Whereas an electric car is completely powered by electricity, a hybrid has both a battery pack and a combustion engine. Hybrids can use both petrol and electric power together, reducing emissions while retaining good mileage and speed.

Because hybrids do have a fuel-powered engine, they do still produce emissions, so they’re not zero-emission vehicles like electric cars are.

What types of hybrids are there?

There are three types of hybrid vehicle you can choose from:

  1. Full hybrid — This is the most common type of hybrid vehicle. Full hybrids — also known as ‘parallel hybrids’ — use both a combustion engine and electric motors to drive the car. They can do so simultaneously or independently; the car can go into full electric mode for short distances at low speeds. The electric motors provide extra power on top of that produced by the engine, so you get better fuel economy.
  2. Mild hybrid — Mild hybrids use a combustion engine and electric motors together just like a full hybrid: the only difference is that they can’t be used independently. Instead, the electric motor is designed solely to assist the engine. The gains are modest, but it’s also the cheapest way to own a hybrid.
  3. Plug-in hybrids (PHEVs) — Plug-in hybrids do exactly what they say on the tin. Just like an electric car, you can plug them in to recharge their electric batteries, which are bigger than they are in a full hybrid. While still powered in part by a combustion engine, you get a much better electric-only range with a PHEV than you would with other hybrids.


Which is best: petrol, diesel, hybrid or electric?

1. Fuel economy

You get more mileage with a diesel engine that you do with a petrol engine. Diesel engines are generally more efficient than petrol engines and should use 15 to 20 per cent less fuel than a petrol engine of the same size.

Electric cars are getting better mileage as the technology evolves, with some of the best electric cars getting up to 300 miles when fully charged. However, that still puts them behind petrol and diesel cars, and home charging can take up to six hours, so they’re not ideal for long journeys.

Hybrids, on the other hand, have the best of both worlds. Their onboard batteries provide extra power on top of their combustion engines, taking you much further with one tank of fuel than you could go with a traditional petrol or diesel engine.

Winner: Hybrid

2. Noise

Petrol engines are usually quieter than diesel engines, but neither of them can compare to the soundlessness of an electric car. In fact, electric cars are so quiet that there are proposals to add artificial engine noise to them in order to make them audible to pedestrians and cyclists.

Hybrid cars are quiet too, but the fact they still have an internal combustion engine means they’re not quite as silent as their full-electric counterparts.

Winner: Electric cars

3. Emissions

Neither diesel or petrol engines are particularly friendly to the environment. Diesel produces fewer CO2 emissions than petrol, while petrol generates fewer additional pollutants like nitrogen.

They both pale in comparison with electric vehicles. Electric cars generate no emissions directly; the only carbon footprint they produce comes from upline emissions involved in the manufacture of the car and engines themselves, plus the emissions required to create the electricity in the first place.

Hybrids sit between the fossil fuel engines and electric batteries in terms of emissions, but ultimately can’t compete with the latter.

Winner: Electric cars

4. Cost

Despite what we know about the pollution caused by petrol and diesel engines, there’s still one major barrier to the electric revolution: the price.

Electric cars are getting cheaper all the time (and many are free of car tax), but they’re still 30-40% more expensive than their petrol equivalents. For a new car, that could be a price difference into five figures; despite the major cost savings on running costs (it costs around £4 to charge an EV enough to go 100 miles), it would take years to make up the cost difference on the initial purchase.

Hybrids are expensive, too. The main reason they cost more than petrol or diesel cars is that their on-board batteries are still very costly to make. This has to be baked into the retail price of the vehicle.

So which is the cheapest option between petrol and diesel? While you get more miles per litre with diesel than with petrol, petrol is generally cheaper, and cars with petrol engines are usually less expensive to purchase and service. Car tax is now often more expensive for diesels because the Government wants to encourage more people to use cleaner alternatives. Finally, the falling popularity of diesel cars means they no longer hold their second-hand value as well as they used to, so you won’t make up as much of your investment if you decide to sell.

Winner: Petrol

Preparing for the journey ahead

Whichever type of car you choose, you’ll want to make sure you’re fully protected for all eventualities. That’s why at Swinton, we offer a range of comprehensive Car Insurance policies designed to cover all kinds of cars, whether that’s an old diesel engine or a state-of-the-art plug-in hybrid.

Find out more about our Car Insurance today.

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