Choosing between petrol and diesel power

Whether to go for 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? To get the facts that will help you decide, plus tips for cutting your fuel costs, read on.

Match your motoring needs

Did you know?

The average motorist will spend more than £100,000 on fuel over the course of a 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, then diesel engine is a good option.

But if most of your 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.

So you’ll need to work out whether 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 may 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.

Comparing petrol and 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.

But there have been big improvements since and now there’s little to choose between petrol and diesel power. We’ve listed 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 that diesel drivers are rewarded with lower tax bands than petrol owners.
  • Economy: Diesel’s greater efficiency means that 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 their petrol counterparts. Diesel fuel is more expensive than petrol and servicing a diesel car may be slightly more expensive.
  • Environmental: Despite its lower CO2 omissions, diesel fuel produces tiny particles that have been 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, so 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 2014 the cost per litre was £1.30 and £1.37 respectively.

The simplest way to cut the cost of your 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 may find that 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.

On the other hand, paying an extra few pence per litre at your closest forecourt can add pounds to your final bill. So it’s important to 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

Read about the different ways you can pay for a car

How to find the right car for your budget

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