Which Car to Buy - Petrol or Diesel ?


Jun 03rd, 2019

Which Car to Buy - Petrol or Diesel ?

Choosing between buying a diesel or a petroleum car can be a mind-boggling decision. Every engine has its advantage over others in terms of the performance, efficiency, operation, and maintenance cost. To make the right decision, you need to define the purpose or reason for getting a car. It can be for personal use, commercial purposes (such as towing heavy loads for long distances) or luxurious (such as cruising or racing). Get a vehicle that best suits your purpose. To make the right decision, you need at least the basics understanding of petrol-powered and diesel-powered cars and their advantages over each other.

Knowing More about Petrol Engines

The Pros

1. Power output - petrol engine cars produce more power than cars with diesel engines of equivalent size. A comparison, for example, BMW 320i 3 Series Sedan (LCI version) has a 2.0-litre 4-cylinder petrol engine with a peak power of 137 kW at 5,000-6,500 revolutions per minute (rpm) and a maximum speed of 235 kilometres per hour (kph). Its diesel equivalent BMW 320d 3 Series Sedan (LCI version) has a lower peak power of 121 kW at 4,000 rpm and a top speed of 230 kph. So if you need power and speed, the petrol engine is your best bet. 

2. Price – petrol-powered vehicles are cheaper than their diesel counterpart. 

3. Fuel price – the cost of petrol is also less expensive than diesel fuel in many countries. 

4. Lower emission of polluting gases – petrol combustion emits more moderate levels of dangerous gases, such as nitrogen. The emergence of hybrid engines and the use of sulphur-free petrol are mitigation measures that reduce the negative impact on the environment. 

5. Smooth and noiseless driving experience – a petrol car has a quieter and smoother drive than its diesel counterpart. 

6. Lighter weight – petrol-powered vehicles are much lighter than their diesel equals. This lightness is one of the reasons why sports cars are mostly petrol-powered. 

The Cons

1. Less efficient than diesel engine – petrol engine consumes more fuel than the diesel engine to do the same work. This higher consumption is the trade-off for the power that petrol engines produce. More power requires more fuel to burn. In our example above, the BMW 320d will consume 4.7-5.2 litres per 100 kilometres while the BMW 320i will consume 7.3-7.9 litres per 100 kilometres travelled on typical urban roads and highways.

2. High carbon dioxide (CO2) emissions - petrol engines release more quantity of CO2 than cars using diesel. In the same example, the diesel BMW (320d) emits 102-113 g/km of CO2 while its petrol equal BMW (320i) emits 128-138 g/km. CO2 has adverse effects on people’s health and the environment. 

3. Low torque - petrol cars are edged out by diesel cars with similar specs because of their lower torque. For this reason, they’re not ideal for rugged terrains, long drives, or harsh weather conditions.

Knowing More about Diesel Engines

The Pros

1. More torque – diesel engines have higher torque or pulling capacity. It’s helpful to remember torque as a diesel engine’s “strength” as opposed to a petrol engine’s “power”. Going back to our example, the diesel BMW 320d has a torque of 400 Newton-metre (Nm) at 1,750-2,250 rpm compared to petrol 320i’s torque of 290 Nm at 1,300-4,250 rpm. With significantly higher torque, diesel cars have better overtaking and towing abilities than petrol cars. 

2. Low fuel consumption – diesel engines are so efficient that they consume 15-20% less fuel than petrol engines do the same work. For example, you get more mileage with a litre of diesel than for the same amount of petrol.

3. High resale value – cars with diesel engines fetch higher resale prices because they have less maintenance cost even for a second-hand unit. They are usually solidly built with quality and durable components. 

4. Low CO2 emission – diesel engines emit way much less CO2 per kilometre covered than their equal petrol engines. They are less harmful to the environment, and as a result, some countries offer tax incentives to diesel cars and diesel fuel. For example, as stated earlier, a petrol BMW (320i) will emit 128-138g of CO2 per kilometre as compared to the diesel BMW (320d) that emits 102-113 g/km. 

The Cons

1. Costlier cars – brand new diesel cars have higher price tags than petrol cars. Their insurance is also higher than for the petrol-powered vehicles by approximately 10-15%. 

2. More expensive fuel and upkeep – while diesel fuel will drive you further in terms of distance, it is usually more expensive than petrol in most countries. Besides, although the repair cost is almost the same, the cost of diesel parts is way much higher than petrol engine parts.

3. Emits higher levels of other gases - despite diesel cars having lower CO2 emissions, their emissions of other nasty gases is higher than in petrol engines. Emissions of particulates and gases other than CO2 is linked to several medical conditions, such as asthma.

4. Noisier than petrol engines – the sounds and vibrations that diesel engines produce are slightly louder and less refined than petrol engines. 

Comparing Petrol and Diesel Engines

If you are still unable to make your choice between petrol-powered and diesel power engine, perhaps comparing the two may shed some light. 


What’s more relevant to you? 

The power and smoothness of petrol or the strength and hardiness of diesel cars? 

  1. If you prefer a silky-smooth drive every time, and your usual trips are short drives around the city, a petrol-powered car would be perfect for you. 
  2. On the other hand, if you cover long distances on a variety of terrains and conditions, then you’re better off with a diesel car. 


What’s your budget? 

  1. For the initial cost of getting a car, the petrol engine is the apparent winner. The petrol version of equivalent models will be cheaper at the local dealership’s showroom. Insurance premiums and taxes on the sale of petrol cars will also be lower.
  2. For the cost of running a car, the diesel engine type wins in the long term. While petrol fuel is cheaper (which is not always the case), diesel fuel delivers more mileage. Diesel-powered vehicles are also more durable. 

Environmental Impact

Which car is friendlier to the environment?

Both diesel and petrol rely on fossil fuels. Back in the days, diesel was considered the dirtier between the two, but that’s not entirely true. 

  1. For lower levels of particulates emitted, petrol wins over diesel by a narrow margin.
  2. For lower levels of CO2 emitted, diesel is the better choice. 

The Bottom Line

Technological advancements have introduced much-improved versions of both diesel and petrol engine cars. Diesel cars are not as noisy or as dirty as they used to be, and petrol cars are becoming more efficient, too. 

The car that you will eventually choose should be one that will serve your purpose. Its specs and features should match your need and intended use. What’s essential is making a well-informed decision, and at Carpart.com.au, we stand with you in the process. We also link you with the leading automotive service providers and quality car part manufacturers and distributors in Australia.