What’s the difference between a diesel and a petrol engine?

To the average driver, there may not seem much of a difference between petrol and diesel, other than the price of a litre when you're standing at the filling station. But petrol and diesel engines can affect how a car sounds, how effectively it runs, and how the car is built altogether. 

First off, the basic difference between petrol and diesel engines is how they process the ignition of their respective fuels. They are both internal combustion engines but operate in a different sequence.  

A petrol engine will combine its fuel with air before being ignited by the spark plugs. On the other hand, the air is compressed in a diesel engine first, and then the fuel is injected. It may not sound like a massive difference, but it does have an overall bearing on how the car primarily functions.

Difference Between a Diesel and a Petrol Engine
Difference Between a Diesel and a Petrol Engine

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What are the pros and cons?

Diesel engines will give you greater miles per gallon than their petrol counterparts because diesel contains more energy, though this is why it will cost you more per litre at the pump.  

Diesel vehicles are most effective for motorway cruising, and you'll return a significantly higher MPG compared to that of a petrol equivalent of the same size.

While this may make it seem like a no-brainer to choose a diesel car over a petrol model, diesel engines are generally larger than petrol engines. 

They need to be fitted in bigger cars to make them more practical and maximise their fuel efficiency. This is why it's rare to see a diesel engine in anything smaller than a mid-ranged family hatchback.  

So, while you might save that bit more when filling up, the extra pounds would generally go towards paying for a larger, more expensive car. 

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Petrol cars with smaller engines will also cost much less to be insured - something that newer and younger drivers are more likely to consider when choosing a new car. Some compact city cars on the market that run on petrol are available with very little, or no road tax to pay whatsoever. 

Suzuki's Dualjet engine technology, for instance, makes their smaller cars, like the Ignis and the Swift, very affordable to run on petrol, while giving you excellent fuel economy and lower CO2 emissions in return. 

Chapelhouse has a large range of high quality New and Used Cars, in which you can choose from petrol and diesel models to best suit your driving needs. You can also find cars that are classed as Mild Hybrids, Self-Charging Hybrids, Plug-in Hybrids and fully Electric Vehicles (EVs). 

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