23th October 2022

Effect of engine size on how long a car lasts

In the UK every vehicle must annually have its safety, roadworthiness and emissions inspected as part of an MOT test. This happens in many countries across the world, but the UK is unique as this MOT data is available for anyone to view and have access to. The quality and quantity of data means many exciting and previously hidden insights can be found by analysing the data. Whilst developing our AI model that predicts how long a car will last we have uncovered some of these insights. Rather than keep these hidden we are sharing some of these insights in this blog.

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Today we are going to look at the effect that a cars engine size has on how long a car lasts. It is generally thought that larger engines are more durable. This is because they are able to generate more torque allowing for a transmission that lets the engine run slower compared to the cars speed. Running slower potentially means less wear and contributes to a longer life. However does the data for UK cars actually support this?

The Results

Lets start by looking at the distribution of engine sizes in UK cars. As you can see nearly all UK cars are less than 3 litres and the majority are around the 1 to 2 litre mark. This is quite a lot lower than American cars which have an average of 2.9 litres. Only a very small percentage of cars had engines greater than 4 litres.

Comparing the miles reached by cars before they are taken off the road it shows a clear upward trend until about 2.5 litres. Supporting the idea that bigger engines are more durable. However beyond 3 litres there is a definite downward trend. This suggests there is potentially a limit to the benefit engine size can have on the longevity of a car. Equally there it could be that cars with larger engine tend to have different purposes causing them to do less miles before being taken off the road.

Looking at how many years on average a car stays on the road reveals a different picture. It is almost an exact mirror image of the distribution of engine sizes. The sizes which are most common, last the least number of years. This again does not support the idea that larger engines are more durable. Of course engine sizes which are less common could suggest the car is unique of specially built for a specific purpose, perhaps encouraging the owners to keep the car going longer.

What about faults? Do cars with different size engines tend to have more faults? We can look more in depth at the MOT histories to get some ideas. When a car takes an MOT test the mechanic may leave some comments on what needs fixing on the car. Whilst not all comments are related to the engine counting the number of comments does give a hint at how many issues there were with the car. The graph plots the average number of comments for a car across its lifetime against engine size. As you can see there is no clear trend with engine size. Again going against the idea that larger engines are more durable.

It is commonly thought that larger engine sizes are more reliable. However there is little real data to support that this is the case in the real world. We think this nicely highlights how important it is to be informed about the specific car you are looking at buying, not just using common advice. All the data and insights we have collected about cars in the UK is available for free to everyone. Just type in a registration number and instantly get all the related data to that specific car and also get a prediction for how long that car is likely to last.

You may be wondering what is it that differentiates the cars that do above average miles and last more years? Over the next few weeks we will look at some of the factors that differentiate cars that last longer. To start next week we will look at how the fuel type of a car effects how long it will last. Follow us on Twitter or LinkedIn to get updates on our posts.