Petrol vs diesel – which car should I buy?

Petrol vs diesel – which car should I buy?

motomatch / 8 July 2021

If you’re in the market to buy a car, it’s probably crossed your mind that you have the option to buy either a diesel vehicle or a petrol one. There is a lot of information out there, and many different opinions on what’s better to drive, but ultimately there are a few hard-core facts that may impact your decision.

First, what is the difference between petrol and diesel engines?

Here’s a little science lesson. Both petrol and diesel engines are internal combustion engines. This means that the “explosion” which causes the energy needed to power the car happens inside the engine; fuel is combined with an oxidiser which creates a reaction. The difference between the two engines is how this happens.

In petrol cars, the air and fuel are combined before being ignited by the sparkplugs. In diesel engines, the air is compressed before the fuel is injected into the engine – this creates a far more powerful reaction and gives the car more “vooma”, as they say.

Which is going to cost me more?

Diesel cars are at least three times more powerful than petrol cars, because of the type of engine they have. As mentioned, the combustion that takes place in a diesel engine is far more violent, and therefore the engines need to be bigger to handle the force. These vehicles are also generally bigger and more robust, so they are more expensive than petrol cars.

Although their purchase price is higher (usually around 10% to 15% more), diesel vehicles have become increasingly popular in the South African market because of their fuel efficiency – you get 30% to 40% more kilometres per litre with a diesel car.

The bigger engines of diesel vehicles also attract a higher insurance premium, and you will need to service these vehicles sooner than you would with petrol cars (around 10,000kms instead of 15,000kms).

How do they compare in terms of resale value?

Diesel cars are not what they were 20 years ago. Improved tech means that you get even more fuel efficiency, a cleaner pollutant output and less noise, making them a lot more appealing to other segments of the market previously untapped. These overall improvements to what was once a powerful but cumbersome vehicle class mean that the resale value of diesel engines has also increased dramatically.

While they are more expensive and appeal to a smaller portion of the market, more and more South Africans are looking for cars with grunt and ground-clearance, so a diesel car makes a great choice, especially a second-hand one because it’s way more affordable than a new one straight off the showroom floor. A diesel car that has been well looked after should be easy enough to turn over.

That being said, the nimble petrol car still dominates the resale market (petrol cars still hold 80% of the market share), because of their obvious affordability. They are easy to maintain and to drive. The practical implications of petrol cars being more user-friendly and accessible to first-time buyers means that they are the first choice for parents of new drivers or students looking for a quick get-around car, so they are always in demand.

All this aside, if a car has been well maintained and cared for – whether it’s a diesel or petrol car – it will attract second-hand buyers.

If you’re looking for information on how to improve the resale value of your car, read our previous post here.

Which diesel cars have the best resale value in South Africa?

It depends on the model, but in terms of resale value, these are the top 3 bakkies in SA:

  • Toyota Hilux
  • Toyota Fortuner
  • Isuzu KB/D-Max

Which petrol cars have the best resale value in South Africa?

  • VW Tiguan
  • Kia Picanto
  • VW Polo Vivo

Are there any environmental impacts to consider?

There has been a raging debate for many years on which engines cause the most negative environmental impact. After doing a lot of research we’ve discovered that both petrol and diesel vehicles are guilty of this, but for different reasons.

Diesel engines emit less CO2 and greenhouse gasses because of the internal efficiency of the engine design. The fuel used in diesel engines has a higher compression ratio than petrol cars (which is what makes it perform better over long distances), so you use less fuel over the same distance. This means that diesel cars emit up to 10% less CO2 than petrol engines in the same category. However, the large amounts of air used in diesel combustion causes more chemical reactions to take place, which leads to other pollutants and toxic particles, such as nitrogen oxide, polycyclic hydrocarbons, ethane and ethylene, being released into the air. Most modern diesel cars come with filters for this exact reason, but because these particles are so refined, they often escape.

Because of the way that petrol engines are built, they emit more CO2, which as we know over time builds up and is toxic for the environment and people. However, they also produce fewer fine particles which directly affect the human body if exposed, particularly the lungs and eyes.

What’s the bottom line?

At the end of the day, it really depends on what you’re going to use the car for. If you’re prone to long-distance trips, over varying terrain or carrying heavy weight, a diesel car is going to be a better option for you.

If you’re looking for something a little easier on the wallet, that can still do the occasional weekend away, but which is mostly used for work and low mileage trips, a petrol car is perfect for you.