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In this article, we take a look at all things mpg, including what it means and how to identify a good mpg rate.
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What is A Good MPG? Average Car MPG Explained

What is A Good MPG? Average Car MPG Explained

In this article, we take a look at all things mpg, including what it means and how to identify a good mpg rate.

  • MPG stands for miles per gallon and refers to the number of miles your car can travel on a gallon (or 4.55 litres) of fuel.
  • The measure helps to determine fuel economy, and normally the higher this number is the better.
  • Figures are determined using the Worldwide Harmonised Light Vehicle Test Procedure (WLTP). This uses lab testing based on real-world driving situations to determine key driving data like mpg and emissions.
  • There are various types of figures listed, with the combined figure being the most commonly used.


When shopping around for a car, whether new or used, you’ll likely have come across mpg. But what exactly does it mean, and how much should it be considered when buying a car?

Read on to become an mpg pro and make a more economical choice with your next car.

What is mpg?

MPG stands for miles per gallon and is used to determine how fuel-efficient a car is. The figure relates to how far a car can travel on a gallon (4.55 litres) of fuel.

For example, say your car offers 50mpg with a gallon of petrol or diesel in the tank. This means you’ll be able to drive 50 miles before running out of fuel.

How is mpg measured in cars?

To work out mpg rates, the Worldwide Harmonised Light Vehicle Test Procedure (WLTP) is used. This replaced the New European Driving Cycle (NEDC) test in 2019, and tests vehicles in a lab using real-world driving simulation.

Vehicles are essentially tested on a rolling road, similar to a treadmill. They are driven in a series of acceleration runs and braking scenarios, at different speeds. This is to gain a wide range of data in different driving situations and on different road types.

The amount of fuel used will be recorded, and then used in a calculation which determines the mpg rate. Although exact mpg rates will vary from model to model, it’s agreed that the higher the mpg the better.

How to calculate your own mpg

MPG figures provided by the manufacturer are of course, only an estimation. Real results will vary across individual makes and models, also depending on how you drive. So, how can you calculate mpg yourself?

There are a few different ways, and one is to use your vehicle’s trip computer. These are fitted in every vehicle to provide a current and long-term mpg reading. You can reset this in your vehicle to get a new reading and see if this changes.

However, if you want a more accurate reading, there’s a helpful calculation you can use. Before using this, you’ll want to fill your car’s tank to full (until the pump handle clicks) and make a note of your mileage.

The next time you fuel up, take note of the amount of fuel you’ve added. This will likely show in litres, so you’ll need to divide this by 4.546 to convert it to gallons. Make a note of the mileage showing on your odometer or trip computer, then divide this by the gallons added to determine your mpg.


50.6 litres � 4.546 = 11.131 gallons

343 miles � 11.131 gallons = 30.814mpg

Why do manufacturers provide multiple mpg figures?

When looking online for your mpg, you may see multiple figures listed. That’s because part of the WLTP test involves using different phases for each type of driving.

Each driving scenario will be given its own rating, followed by a combined figure at the end providing the average mpg. These are the phases used in the test to simulate different types of driving:

  • Low – driving in urban areas at around 35mph (56.5km/h)
  • Medium – driving in suburban areas up to 48mph (76.6kw/h)
  • – driving through rural areas at around 61mph (97.4km/h)
  • Extra-high – motorway driving at speeds of around 82mph (131.3km)
  • Combined – the average figure used when considering all of the above.

Remember, actual results will vary depending on the specific car you drive (including any extras fitted), and how you drive it.

How can I improve my car’s mpg rate?

You may be wondering, ‘Can my driving affect my car’s mpg?’, and the answer to that is yes.

Harsh acceleration and braking are known to reduce your car’s mpg, making it burn fuel less efficiently. Other good practices you can use to help maximise your mpg include:

  • Avoid using the air conditioning
  • Remove any roof boxes or bars that could make your car heavier
  • Take out any unnecessary items from your boot
  • Keep tyres fully inflated to the correct pressure at all times
  • Use as high a gear as possible and reduce revs in between changes
  • Use cruise control only on motorways
  • Avoid frequent shorter journeys

Also known as ‘hypermiling’, using these techniques is sure to bring you small savings in fuel. Each of which adds up over time!

What’s the difference between mpg and l/100km?

Litres per 100km (l/100km) is another figure you may have seen listed elsewhere. This is the European measure for fuel efficiency and works differently to mpg. With l/100km, the lower the number the better.

If you’re unsure what this means in mpg terms, don't worry. Dividing the figure by 282.5 will give you the mpg figure for your car.

What is a good mpg on a used car?

Generally, the higher the number the better. For a used car, it’s agreed between 40-60mpg is a good indication.

Choosing a car with a good mpg

Now you know how it works, how do you then choose a car that provides a good mpg? As we saw earlier, the general rule of thumb is the higher the mpg, the more fuel-efficient the vehicle is.

With this in mind, check out our article on the most fuel-efficient cars to drive for some inspiration. If you’re looking for a used car specifically, read about why mileage matters when buying a used car.

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Plus, with our flexible finance options, you can spread the costs in a way that suits you. Contact our friendly team today, or book an appointment at your local dealership.

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