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Petrol and Diesel Explained

By: Tracy Wilkinson - Updated: 22 Sep 2010 | comments*Discuss
Petrol And Diesel Explained

Ask any motorist what kind of car they have, and although they might not know the full make and model details - in most cases, they'll know whether or not their engine is petrol or diesel powered. But many drivers have no idea what the differences are between the two or which is the best one for them to buy so we’ve put together a guide that explains the differences for you.

Diesel Powered Engines

Diesel is produced through a process of distilling crude oil and is then burned in an internal combustion engine. For many years, diesel powered cars were seen as the most economical choice as when it came to filling up the tank, diesel was always cheaper than petrol at the pump. This has changed in recent years, but despite this a lot of motorists still swear by diesel because it has good fuel economy – usually better than petrol.

Why Choose Diesel?

Diesel is often the preferred choice of taxi and lorry drivers because of the good fuel efficiency and also because it enjoys lower Co2 emissions than petrol powered engines. This can save motorists even more money now that the vehicle excise duty is worked out on the amount of carbon dioxide that a vehicle produces, rather than the size of its engine.

Is it Easy to Buy?

Most petrol stations sell diesel but depending on the size of the fuelling station it is usually sold through less pumps compared to unleaded petrol. It’s not hard to get hold of although you might have to queue a bit longer at the pumps.

What's the Downside of Using Diesel?

Although the Co2 emissions are lower than with many petrol engines, diesel produces a lot of tiny particles into the air which have been linked with high levels of pollution and can cause and add to respiratory problems. Many experts consider diesel cars to be far more polluting than petrol engines but fitting catalytic converters and particle filters can help to address these issues.

Diesel cars are usually priced higher than petrol powered cars of a similar specification and also cost company car drivers more as diesel engine cars attract higher tax bills than those that run on petrol. Diesel is also a concern for environmentalists and those who wish to live a 'greener' lifestyle as it is not sustainable - the diesel supply will run out one day.

Petrol Powered Engines

Like diesel, petrol is produced through a process of distilling crude oil and is then refined and burned in an internal combustion engine, producing power.

Why Choose Petrol?

Petrol is the most widely available fuel - it's available at over ten thousand UK locations and is relatively affordable. A better awareness of environmental issues has led to car manufacturers producing 'greener' cars which have better fuel consumption and lower Co2 emissions.

What's the Downside of Using Petrol?

Unfortunately, petrol engines are still responsible for producing high levels of carbon dioxide. They are also less fuel efficient than equivalent diesel models, and petrol, like diesel will run out one day as it is not a replenishable resource.


Both diesel and unleaded petrol cars are going to be important in the future of motoring because a lot of new technology is concentrating harder and harder on getting more fuel efficient and environmentally friendly engines into production. Oil companies are trying to come up with ways to remove sulphur from petrol and if they can manage this, car manufacturers are committed to providing cleaner engines. In the meantime the focus on greener cars is likely to push petrol and diesel hybrids to the top of the pile for economical, fuel efficient and cleaner vehicles.

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