When choosing a new car, it’s important to consider what type of engine is best for you – petrol or diesel? If you’re confused about the differences, we explain all below, so you can choose the right option for your driving needs and your bank account.
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How do petrol and diesel engines differ?
Petrol and diesel vehicles both use internal combustion engines. These combine fuel with an oxidizer to create the energy that powers the vehicle.
Petrol and diesel engines differ in the way that the combustion occurs. In a petrol engine, the fuel is combined with air and then ignited by spark plugs. In a diesel engine, fuel is injected into compressed air and ignited due to the high temperatures caused by the compression.
What to consider when choosing between a petrol and diesel engine
Because petrol and diesel engines work in slightly different ways, they can bring different benefits and disadvantages to driving and maintenance.
In general, diesel cars are more expensive to buy than petrol cars. Prices can range though, and often the difference in price won’t be very much.
One of the reasons diesel cars are often more expensive than petrol cars is because the engines have to be stronger to withstand the high pressures of compression.
Diesel cars can generally be more expensive to run than petrol cars. Their repair costs are usually higher, although this will depend on the specific car, and as such, insurance rates for diesel cars are also higher.
Regular services for a diesel car are often more expensive than petrol cars, as diesel cars will have more systems that need to be checked and maintained.
This can include AdBlue, an emission-control system that many modern diesel cars utilise. This system uses an ammonia-based liquid to help reduce NOx emissions from the car. The AdBlue will need refilling, but the cost is usually quite low.
One area where diesel outperforms petrol in terms of costs is with fuel. Diesel cars are usually much more fuel efficient than petrol vehicles. Diesel drivers can save money when it comes to fuel, even with diesel being more expensive to buy than petrol.
Diesel cars are also usually a little cheaper than petrol cars when it comes to tax. Car tax is worked out on CO2 emissions, and as diesel cars are more fuel efficient, their car tax is usually lower.
Diesel and petrol cars have a few differences when it comes to driving performance. Diesel cars have great torque, which makes them great if you will be towing and/or driving on the motorway regularly.
Petrol cars are quieter than diesel cars, producing much less noise pollution. More modern diesel cars have improved in this regard but will likely still be louder than their petrol counterpart.
Emissions and the environment
If you want to consider the impact on the environment from your car, then there is a clear winner between petrol and diesel. While diesel cars do have better fuel efficiency and so produce fewer CO2 emissions, they produce NOx emissions, which are much more dangerous.
Of course, if you really want to lessen your impact on the environment, your best choice is an electric vehicle. It’s worth bearing in mind that from 2030, no new diesel or petrol engines will be produced – only electric and hybrid vehicles, or second-hand petrol and diesel cars will be bought.