Published 6 May 2025
Fuel for thought: Petrol vs diesel
Buying a new car comes with a world of choices, but one of the first decisions you’ll need to make is whether the car is petrol or diesel…
- What’s the difference between petrol and diesel?
- Which is more cost effective: Petrol or diesel?
- Should I be using petrol or diesel?
What’s the difference between petrol and diesel?
There are some key differences between petrol and diesel.
Diesel cars are more economical compared to their petrol-powered versions.
Petrol engines are smoother, and they deliver more performance and/or horsepower, while diesel has a higher energy density than petrol so it has the ability to go further while using less fuel.
Does diesel cost more than petrol?
Generally speaking, diesel powered cars are slightly more expensive to buy. Diesel is also around 10p a litre more at the pumps, however, diesel cars are more economical - so in the long run you’re more likely to make savings running on diesel rather than petrol.
From 1 September 2015, diesel cars legally had to be sold with an additive called AdBlue - this helped to reduce the emissions released by diesel engines. So, if you own a diesel car registered before this date then you’re more likely to be charged when entering a city centre such as ULEZ in London.
If you’re looking to buy a second-hand car and you live or drive to places such as Birmingham or London, this should be a cost consideration.
Should I use petrol or diesel?
Petrol and diesel both have their advantages and disadvantages, and a lot of them come down to personal preference.
Some drivers prefer economy over power, others like having a little bit more power. Bigger cars such as SUV’s, pickup trucks and some estate/saloon cars will either have diesel as standard or a common option, while hatchbacks, smaller cars and performance cars are more likely to be offered with petrol engines.
Standard fuel vs premium
Firstly, let’s take a look at petrol, as there’s a difference between premium petrol and premium diesel. In the UK, there are typically two different octane rated fuels available: E5 and E10. The E stands for Ethanol and the number shows how much ethanol is mixed in the fuel as a percentage, i.e. 5% and 10%.
E10 arrived in UK petrol stations on 1 September 2021. Most modern cars are designed to run on E10 fuel, which is usually the more cost-effective option at the pump. The ethanol is typically made from renewable sources such as sugar beet or corn, which makes the fuel more environmentally friendly.
Premium diesel is slightly different but follows a very similar idea. It contains a chemical called cetane, a substance which helps to increase the compression point of the diesel. So, generally, the higher the rating of the diesel, the more expensive it is.
Again, with most diesel cars on the road, the standard fuel is more than suitable for your car.
Different brands of premium fuel will claim to have different benefits to your car. Some premium fuels will claim to lower your fuel consumption, while others say that it can help clean out your engine. Most will claim to increase performance, but this is heavily debated, and the only noticeable difference will be in performance or sports cars.
So, overall it’s up to you whether you choose a petrol or diesel car - both have their benefits and draw backs, but it’s always worth considering cost, environment and where you drive. Remember though, there's a plan to ban the sale of petrol and diesel cars in the UK by 2030, so it's worth considering this in your decision making...
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