Petrol vs Diesel | GO Vauxhall

Petrol vs Diesel - what option is best for you?

Available at GO Vauxhall London, South East England

The controversial subject of petrol versus diesel has been debated for many years. When you choose a new car, one of the biggest decisions you need to make is whether to opt for a petrol or diesel engine.

So what is the difference?

The chemical make-up of petrol differs from diesel. Diesel fuel is denser than petrol and contains as much as 13% more energy than an equivalent amount of petrol. There are also some differences in the methods used for burning petrol and diesel in a combustion engine.

In a diesel, air is pushed into the engine’s combustion chamber and heated by compression to over 425°C. Fuel is then pressure-injected into the chamber, where it mixes with the hot air and becomes hot enough to ignite.

A petrol engine is different because the fuel and air are mixed before they go into the chamber to be compressed. Compression is lower-ratio than in a diesel engine to ensure the fuel does not automatically ignite. Instead, a spark is used to ignite the blend of fuel and air.

Why choose petrol?

  • The price of a litre of petrol is cheaper than the price of diesel.
  • Petrol cars are usually cheaper than the diesel equivalent.
  • In recent years petrol cars have become more fuel efficient, gradually closing the gap in fuel economy between petrol and diesel engines.
  • There are lower rates of nitrous oxide emissions from petrol engines than diesels.
  • Petrol engines tend to be quieter than diesels.
  • Filling up your tank with petrol can be less messy than diesel (some people choose to use disposable gloves to avoid getting diesel on their hands at the pump).

Disadvantages of a petrol engine

  • CO2 emissions are higher from a petrol engine.
  • A petrol engine will generally not be able to do as many miles before it requires significant maintenance or replacement.

Why choose diesel?

  • You will get good fuel economy from a diesel engine, particularly turbo versions.
  • Good fuel economy means you have longer range between refuelling, so you make fewer trips to the pump. This can be particularly helpful on long journeys.
  • You won’t need to visit the garage for routine maintenance so often, thanks to the longer service intervals for diesels.
  • Maintenance costs may be lower, as some of the specialist parts in a petrol engine are not used in a diesel engine. For example, a diesel engine does not have spark plug ignition, which in a petrol engine may need tuning and replacing.
  • Diesel engines are ideal for towing as torque is usually greater from a diesel than from an equivalent sized petrol engine.
  • Diesel cars have generally retained their value better than their petrol counterparts. Large diesel engines are particularly likely to have low rates of depreciation. However it is not clear whether this will continue to be the case as contributing factors, such as tax rates for diesels are set to increase in 2018, following the changes announced in the autumn 2017 budget.
  • Diesel engines have lower CO2 emissions than petrol engines.
  • Some diesel engines can also use biodiesel fuel, for a more environment-friendly option. However, it is important to check that the diesel engine in your car is suitable for biodiesel. Newer diesel cars will generally need to use a bend of biodiesel and standard diesel.

Disadvantages of a diesel engine

  • Diesel usually costs more per litre than petrol.
  • You won’t see the fuel economy benefits of a diesel engine unless your lifestyle involves a lot of dual carriageway or motorway driving.
  • If you drive only short journeys, particularly those under seven miles, there is an increased risk of the particulate filter getting blocked. The cost of rectifying this can be expensive. If this is the type of driving you do, a diesel may not the be ideal choice for you.
  • Diesel engines can be noisier than petrol, so if you prefer a quiet engine, make sure you choose a refined engine model.
  • The changes announced in 2017 relating to car tax mean that the significant tax savings for purchasing a new diesel will no longer be available. In the autumn 2017 budget, the chancellor announced that new diesel cars registered from 1st April 2018 will incur additional charges at a rate determined by their CO2 emissions band. For full details of the tax rates payable for new diesel cars visit the government website:

There are advantages and disadvantage to either engine type. Your decision on whether to opt for a petrol or diesel comes down to which type of engine is most suitable for your driving