What car engine size do I need?

You might find it easy to decide whether your new car needs air conditioning or a leather interior, but picking the right engine size might be slightly more tricky. We’re looking at different engine sizes to help you work out what capacity you need.

Want to understand the ins and outs of gearbox choices? Check out our guide to manuals and automatics. Struggling to tell your straight-six from your V8? Read our car engine types guide.

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How can you tell the size of an engine?

Engine sizes in the UK are measured in either litres or cubic centimetres (cc) – 1,000cc equals one litre. This describes the amount of space inside the engine’s cylinders where power is produced. As a rough-and-ready rule, the more space there is, the more power you’ll have.

That’s why city cars such as the Skoda Citigo use a tiny 1.0-litre engine to move them around, while the high performance Ferrari F12 uses a 6.3-litre unit to achieve its 217mph top speed.

It’s worth bearing in mind that older cars usually have bigger engines, but it isn’t quite fair to compare them to new cars. Technology moves at such a rapid rate that the latest vehicles can easily make the same power from smaller engines.

No replacement for displacement?

It isn’t as simple as ‘bigger means better’, however, because many modern engines use turbochargers to squeeze extra power from a smaller size. The BMW i8, for example, uses a surprisingly small engine – 1.5-litres in this case – mated to a turbocharger and electric motors to make roughly the same power as the 3.0-litre M3.

A decent rule of thumb is to consider turbocharged engines as equivalent to non-turbo ones that are about 50 per cent larger. For example, Ford’s 1.0-litre EcoBoost replaced the firm’s previous 1.6-litre engine, while Mercedes replaced its 6.3-litre AMG unit for a twin-turbo 4.0-litre one.

What about diesels?

The type of fuel pumped into the engine also affects how much power is produced. Diesel cars tend produce less power compared to equivalent petrols, so they’re often larger in capacity and rely on turbochargers to achieve similar figures.

Diesels usually produce more torque than petrols so, even if their headline horsepower figures aren’t as high as similar petrol engines, they can feel just as fast in everyday driving.

What will you be using your car for?

The size of the engine you really need depends on two things – what your car will be used for, and how big it is.

If you only need a car to pop to the shops, to brave the school run or if you spend the majority of your time in towns and cities, you’re unlikely to need anything larger than a 1.4-litre. Indeed, many manufacturers are producing 1.0-litre turbocharged engines that are perfect for light town use.

If you spend more time driving on motorways, you’ll find anything from a 1.4 to a 2.0-litre will do an adequate job. A larger, more powerful engine will feel less strained on the motorway, require less encouragement for overtaking and, in some cases, be more efficient at constant speeds than a smaller engine that’ll have to work harder.

If you intend to tow a trailer, you’ll definitely want a diesel engine – some SUVs offer 3.0-litre six-cylinder diesels that are ideally suited to the job. Anything larger than 2.0-litres will, for most, be a case of ‘want’ rather than ‘need’ – of course, if you enjoy driving, there are few pleasures more childish and indulgent than flooring the throttle on a very powerful car.

The size of car has an effect on the engine you’ll need, too. City cars and superminis such as the Renault Clio are small and light so only need engines ranging from 0.9 to 1.4-litres. Family hatchbacks such as the Ford Focus use anything from 1.0 up to 2.0-litres. Compact executive cars like the Jaguar XE have capacities ranging from 2.0 to 3.0-litres, and anything larger could use an engine larger than 6.0-litres.

For the stat fans

So which cars stand at either end of the capacity charts? The Caterham Seven 165 currently has the smallest engine on sale in the UK – a tiny 660cc turbo unit – while the largest belongs to the Bentley Mulsanne and its 6,752cc “six-and-three-quarter-litre” V8.

Find out more

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