Money Advice Service

Choosing petrol or diesel power is one of the first decisions you’ll have to make before buying a new car. What’s going to be best for your type of motoring, for the environment and your wallet? Here you can get the facts to help you decide and tips for cutting your fuel costs.

Which is better based on your motoring needs

Did you know?

The average motorist will spend more than £100,000 on fuel over their lifetime − petrol and diesel being the biggest motoring expense of all.


From a financial perspective, there’s now less and less difference between a petrol and a diesel car.

It is still true that if you look at pure fuel running costs, a diesel will cost less. You will, though, have to have high annual mileages and use motorways frequently to get the financial benefits.

This is because newer diesel vehicles now have higher tax, which can cost almost as much as the fuel savings you could make in a year, and there are also concerns over air pollution caused by diesels. Take a look at the car tax prices to see if the vehicle you have in mind could be affected.

Need to know

The sale of new diesel and petrol cars will be banned in 2040. That means in the coming years, there will be a significant change in the types of vehicles we’ll be driving, how much traditional? cars are worth, and even financial encouragement to buy alternative fuel vehicles like electric cars.

It’s also true that a diesel vehicle will typically cost more than the equivalent petrol car. Diesel fuel also costs more than petrol.

So you’ll need to work out if this saving in fuel consumption will offset the extra expense of a diesel car and its running costs.

For example, if you drive a diesel car more than 12,000 miles a year, you might recoup £1,000 in a couple of years two.

But if your mileage is around 6,000 miles a year it could take you about four years to recoup the same amount.


Research from Which? shows that for new diesels it can take between six and 11 years to recoup the extra cost of a diesel over a petrol car.

With the new rules around taxes on diesels, and some cities such as London due to increases in charges to penalise diesels, resell values of diesels is also expected to be lower, especially if you might change cars in the next five years.

That means that if most of your journeys are local and your mileage is lower, a small petrol car might be more suitable for you, especially if you’re looking to change vehicles in the next five years.

Also, keep in mind that newer diesels have a special filter fitted to help prevent pollution. It’s called a diesel particulate filter (DPF). These can clog if the vehicle isn’t used regularly on a motorway, and is costly to fix or replace. This means if you don’t use motorways often, a diesel might not be for you.

Compare diesel and petrol car running costs at the Which? Car website.

Petrol versus diesel cars

Top tip

To find out how much your car costs to run, try our Car costs calculator tool.

There used to be a negative perception that diesel cars were slower, smellier, noisier and more expensive than petrol cars.

There are, though, still some large differences in the characteristics of cars using the different fuels that make them suitable for different uses.

Take a look at the pros and cons of each below.

Pros of diesel

  • Financial: diesel engines are more efficient and use 15−20% less fuel meaning cheaper running costs. The cars historically have tended to have a slightly higher resale value too, but this is changing with time.
  • Environmental: lower CO2 emissions means that diesels from before April 2017 get a lower tax band than petrol engine cars. For newer diesel cars though, tax is typically higher than for petrol.
  • Driving experience: diesel cars offer more low-speed torque which means they have better overtaking power and towing ability.

Cons of diesel

  • Financial: diesel cars usually cost more than petrol. Diesel fuel is more expensive than petrol and servicing or fixing a serious problem on a diesel car might be slightly more expensive. New diesel cars also cost more to tax than petrol cars, and depreciation is now slightly higher. There are a number of new charges, such as the London T-Charge and Ultra Low Emissions Zone, that will make it more expensive to drive diesels in certain cities.
  • Environmental: despite lower CO2 emissions, diesel fuel produces tiny particles linked to breathing disorders such as asthma.
  • Driving experience: diesel engines tend to be slightly noisier, but this problem is improving.

Pros of petrol

  • Financial: petrol is cheaper than diesel fuel and the cars tend to be slightly cheaper to buy and service.
  • Environmental: While CO2 emissions are higher than diesel, petrol cars produce less of some other dangerous emissions like nitrogen.
  • Driving experience: petrol engines tend to be less noisy.

Cons of petrol

  • Financial: engines are less efficient and use more fuel than diesel.
  • Environmental: petrol engines emit more CO2 than diesel cars.
  • Driving experience: Petrol engines need the driver to change gear more regularly, for example when overtaking, to make the most of the engine’s power – but some people will actually prefer this style of driving.

Find the cheapest fuel

Did you know?

In 1989, the average cost of unleaded petrol was 38.5p per litre and diesel 36.1p per litre. By 2018 the cost per litre was 121.7p and 124.4p respectively.

The simplest way to cut the cost of everyday motoring is to buy your petrol or diesel from the cheapest service station in your area.

Visit to compare the fuel prices at forecourts in any postcode.

You can also calculate your annual fuel bill and sign up for an email alert to keep up to date with the latest fuel prices in your area.

Top tip

Supermarkets often run petrol promotions offering discounts of 5p-10p off each litre of fuel if you spend a certain amount (for example £30) shopping in-store.

You get a voucher to use at the supermarket’s service stations.

You might find supermarkets in your area offer a good price on fuel, but be careful not to add miles to your journey just to save a penny a litre.

However, paying an extra few pence per litre at your closest forecourt can add pounds to your final bill.

So, weigh things up carefully when looking at cheapest versus nearest.

Find out the true cost of your car journeys at the website.
Find out how to reduce your transport costs and lower your carbon footprint on the Energy Saving Trust website.

Your next step

For more information read the articles below:

This article is provided by the Money Advice Service.