Choosing between petrol and diesel power

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.


Generally speaking, if you cover a high mileage and most of your driving is on motorways, diesel is a good option to buy as it will be more economical than cars with petrol engines.

But if most journeys are local and your mileage is lower, a small petrol car might be more suitable for you.

Diesel cars and diesel fuel are slightly more expensive, but more fuel-efficient and could save you more money in the long-term.

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

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

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

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 diesel cars were slower, smellier, noisier and more expensive than petrol cars.

But there have been big improvements and now there’s little to choose between them.

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. The cars tend to have a slightly higher resale value.
  • Environmental: lower CO2 emissions means diesel drivers are rewarded with lower tax bands than petrol owners.
  • Economy: diesel’s greater efficiency means its CO2 emissions are 20% lower than petrol.
  • Driving experience: diesel cars offer more low-speed torque so 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 a diesel car might be slightly more expensive.
  • Environmental: despite lower CO2 omissions, 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.
  • Driving experience: petrol engines are more refined and less noisy.

Cons of petrol

  • Financial: engines are less efficient and use more fuel than diesel, and the cars depreciate slightly more.
  • Environmental: petrol engines emit more CO2 than diesel cars.

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 2016 the cost per litre was £1.09 and £1.10 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 onto 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 websiteopens in new window.

Your next step

For more information read the articles below:

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