Which car to buy... petrol or diesel ?


Jun 03rd, 2019

Which car to buy... petrol or diesel ?

Which car to buy - petrol or diesel engine?

Finding the perfect car entails due diligence and major decision-making on your part. One of the first questions to ask is this: Which engine type do I want my car to run on? Will it be an engine fueled by petrol or diesel? Your answer is crucial because it will not only have a big impact on the performance, efficiency, and maintenance of your car, but also on the cost of operating it. 

To make an intelligent decision, always keep in mind your reasons for getting a car. It could be for personal use to make moving easier, such as getting to and from your workplace or your children’s school. It could be for commercial purposes, towing heavy loads, or driving long distances. The best car is the one that matches your reasons for buying one. So as we differentiate between petrol and diesel-powered cars, never lose sight of that purpose.

Knowing More about Petrol Engines

The Pros

1. High power output - petrol engine cars produce more power than cars with diesel engines of equivalent size. A comparison between cars produced for both types of engine will confirm this. Here’s an 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 for 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, petrol engine is your best bet. 

2. Less expensive – petrol cars are generally priced lower than their diesel counterpart. 

3. Cheaper fuel – the cost of petrol is lower than diesel fuel, too. 

4. Low emission of some dangerous gases – burning petrol emits lower levels of some dangerous gases, such as nitrogen. The emergence of hybrid engines and the use of sulfur-free petrols are also seen as mitigating factors that reduce their negative impact to the environment. 

5. Smooth and noiseless driving experience – a petrol car will have a quieter and smoother drive than a similar car running on diesel. 

6. Lighter weight – this is one of the reasons why sports cars will always be built with petrol engines. They’re so much lighter than the diesel type. 

The Cons

1. Less efficient than diesel engine – petrol engine consumes more fuel than diesel engine does. This is the tradeoff 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 kilometers while the BMW 320i will consume 7.3-7.9 litres per 100 kilometers travelled on typical urban roads and highways.

2. High carbon dioxide (CO2) emissions - cars with petrol engines release higher quantities of CO2 than cars using diesel. High CO2 levels have a negative impact on people’s health and the environment. In the same example above, the diesel BMW (320d) emits 102-113 g/km of CO2 while its petrol cousin (320i) emits 128-138 g/km. 

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 BMW example, the 320d has a torque of 400 Newton-metre (Nm) at 1,750-2,250 rpm compared to 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. In other words, you get more mileage with a litre of diesel for the same amount of petrol.

3. High resale value – cars with diesel engines fetch high resale prices due to the fact that they cost less to run even as secondhand units. They are heavily built, too, with expensive and durable components. 

4. Low CO2 emission – they are less harmful to the environment, and some countries offer tax incentives to diesel cars and diesel fuel.

The Cons

1. Costlier cars – brand new diesel cars have higher price tags than petrol cars. Their insurances, too, cost around 10-15% more. 

2. More expensive fuel and upkeep – while diesel fuel will bring you farther in terms of kilometers, it is also more expensive than petrol. The cost of repair services for both diesel and petrol engines don’t differ so much, but their respective parts do. Diesel engine components are often more expensive than those of a petrol engine.

3. Emits higher levels of other gases - although diesel cars have lower CO2 emissions, the same thing cannot be said of the other nasty gases they emit. Emissions of particulates and gases other than CO2 have been linked to several medical conditions including asthma.

4. Noisier than petrol engines – the sounds and vibrations that diesel engines produce are slightly louder and less refined than those of petrol engines, even to this day.  

Comparing Petrol and Diesel Engines 

Both types of car engines have their fair share of advantages and disadvantages. At this point, you’re probably feeling confused and overwhelmed by the many choices out there. Like we said earlier, you have to keep your sights on your original purpose for buying a car. Let’s have one last look at the two engine types as we set them side by side. 

1. Performance

Which one is more important 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 normal trips are short drives around the city, a diesel 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. 

2. Economy 

Which car type comes out cheaper after crunching the numbers?  

  1. For the initial cost of getting a car, the petrol engine type is the obvious winner. The petrol version of equivalent models will be cheaper off your local dealership’s showroom. Insurance premiums and taxes on the sale of petrol cars will be lower, too.
  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. Other future expenses should also be included in the picture, such as maintenance cost. 

3. Environmental Impact

Which car is friendlier to the environment? Both diesel and petrol come from fossil fuels. Back in the days, diesel was considered the dirtier between the two, but now 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 opened the gates for 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 important is that you’re making a well-informed and thoughtful decision before choosing between a petrol and diesel-powered car.