Diesel vs petrol: What’s the difference?

In the game of diesel vs petrol, which fuel wins out? The truth is, this isn’t a straightforward contest. When weighing one option against the other, your needs, priorities, and budget will all come into play. Read on to find out what to consider when making your choice.

First up, what exactly are these fuels? 

Petrol

Petrol, petroleum, or crude oil is a fossil fuel made up of hydrogen and carbon. It comes from the remains of ancient plants and animals. Over millennia of heat and pressure, this flora and fauna turn into substances packed with carbon that we can use for various activities, including as a fuel. 

Because they’re a non-renewable resource (meaning once they’re gone, they’re gone), fossil fuels may not be able to fulfil our needs forever. They’re also the primary source of human emissions into the environment, and a major contributor to climate change.

Diesel

Diesel is a type of fuel that works in compression ignition engines, commonly known as diesel engines. Larger vehicles such as trucks, trains, tanks, buses and boats use diesel, as do some cars and construction vehicles. 

Diesel is most commonly made from petrol through a fractional distillation process, meaning it is distilled, compressed and separated into parts. It can also be made from biomass, renewable sources derived from plants and animals. Innovations in this kind of technology are constantly being made to answer the global energy crisis.

Is it better to get diesel or petrol?

So, is diesel better than petrol? Unfortunately, there’s no simple answer to this, but which you use to run your car is a decision you’ll have to make when you buy a new vehicle. Petrol isn’t suitable for diesel engines, and vice versa. In fact, putting the wrong fuel in the engine can cause damage to your engine.

So if you’re wondering, “Should I buy a petrol or diesel car?”, the answer depends on what you need to accomplish with your vehicle and your budget.

We’ll take you through the FAQs that will help you decide the best option for you. 

Is petrol or diesel cheaper?

Historically, diesel has typically been more expensive than petrol. 

According to the AA, the average prices were as follows at the end of September 2023:

Petrol: 155.5p/litre

Diesel: 159.4p/litre

Prices are not centrally regulated in the UK. It’s up to individual retailers to set their own price, which means the cost can vary from one outlet to another and from one day to the next. It’s important to note, however, that all fuel sources are taxed the same by the UK Treasury.

Diesel cars tend to be more expensive to buy, too. Even though petrol vehicles tend to be more popular for personal use, diesel is used in many commercial vehicles, which increases demand.

But price isn’t the only factor to consider here.

Does diesel last longer than petrol?

Diesel cars tend to be more efficient than their petrol counterparts. That means that while you’re paying more for fuel at the pump, that fuel may get you further. This makes diesel vehicles a great option for long-distance travel as it means fewer refuelling stops.

Why is a diesel engine better than petrol?

Not only will a diesel engine typically get you further before it’s time for a refuel, it’ll also provide you better performance at lower revs. That means you can use higher gears at lower speeds.

Because of their fuel efficiency and performance advantages, diesel engines are often used to pull heavy loads. We say they have better torque, which means they have better pulling power.

If you’re using your vehicle for machinery or off-road purposes, you may know that you’ll be opting for red diesel. If, on the other hand, you’re using diesel in your car, you’ll likely be using white diesel. For a lowdown on the diesel types, head here. (Spoiler: they’re not that different!)

What is the disadvantage of diesel cars?

Diesel vehicles tend to be more expensive than petrol ones. That’s because the hardware that makes up a diesel engine is pricier. This can affect your:

Initial purchase price

Servicing costs

While diesel cars are great for long trips and carrying heavy loads, if you’re looking for a car to buzz around town in, petrol may be a better option. Petrol cars respond more readily to a gear change and offer you quick acceleration if you need it.

If you live in a cooler climate, it’s important to note that your diesel vehicle may have lower frost resistance as diesel is prone to gelling when it’s very cold. Gelling is where wax particles form in the fuel, and it freezes, meaning that it can’t flow through the engine. 

While diesel cars have historically been touted as more environmentally friendly due to their supposedly lower carbon emissions, recent findings have shown that this may not actually be the case. 

Through what has been termed “Dieselgate”, Volkswagen and many other car manufacturers were shown to be using a “defeat device” in their vehicles that lowered the readings of vehicles’ emissions. The result is that the environmental impact of diesel cars has been severely underreported.

Read more: Diesel claim process: All you need to know

So does that mean that diesel cars are as bad when it comes to emissions as petrol vehicles? It depends on the vehicle. Newer diesel engines do, in fact, boast lower tailpipe emissions. Many diesel vehicles also now use an exhaust fluid called AdBlue, which helps to lower the toxicity of emissions.

Should I just go electric instead?

As electric cars and hybrid vehicles become increasingly popular, you may wonder if it’s not a better idea to ditch the fuel completely — and there are certainly good reasons to do so.

Electric vehicles come with all sorts of benefits, including:

Less impact on the environment as there are no tailpipe emissions

Lower running costs

No, or reduced, car tax

No congestion charge in clean air zones

Financial perks, like government grant schemes that help you switch over

Less noise — they’re quieter than their petrol and diesel counterparts

Better parking options — you may have noticed the dedicated spots for electric vehicles popping up all over the place

In an effort to transition to renewable fuel sources, Britain is set to ban new petrol and diesel cars by 2035. You will, however, still be able to purchase second-hand petrol and diesel vehicles after that, so they won’t be disappearing off the roads completely. The goal is to facilitate a national move towards electric vehicles. 

If you’re not ready to go electric, another option is LPG conversion. LPG stands for liquid petroleum gas. While LPG is also a hydrocarbon fuel, it can store a lot more energy in this liquefied form, making it a more sustainable option. LPG conversion is taking a car that runs on either petrol or diesel and converting it into a dual tank that runs on both LPG and petrol or diesel.

Read more: Five things to know before you buy an electric van

In summary

If you’re deciding between a petrol and diesel vehicle, here are the important factors to look at:

Purchase cost: Diesel vehicles and diesel as a fuel tend to be more expensive.

Maintenance costs: Diesel vehicles usually top this list, too!

Better fuel economy: Diesel will give you more distance per litre.

Performance: Diesel vehicles have better torque, making them ideal for pulling heavy loads. Petrol vehicles, on the other hand, make for a peppier urban vehicle.

Emissions: Well, this is a tricky one. They both release carbon emissions. While diesel has historically been seen as the lesser of the two evils, recent findings showed that diesel emissions may be higher than estimated.

Climate: Diesel can gel up in colder climates.

Then, of course, you might want to ditch the petrol-diesel debate altogether when buying a new car and opt for an electric vehicle. There are many advantages here, including environmental sustainability, lower running costs, and government financial perks.

It’s also important to remember that the UK is in the process of phasing out new diesel and petrol cars. Looking ahead, this might make electric vehicles a more popular option. 

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