Pros and cons of Diesel Engines

In Australia, petrol engines have long been the go-to for the majority of family cars. Besides trucks and 4WDs, diesel cars are fairly rare on Australian roads compared with places like Europe, where diesel vehicles account for about 50% of cars on the road. However, that is changing as diesel technology progresses and perceptions of diesel as a “dirty fuel” continue to change.

If you’re trying to decide whether to buy a diesel or petrol car, it’s worth weighing up the pros and cons. There is no clear cut answer regarding which is best, so your choice should depend on a variety of factors including how much you drive, the type of driving you do (e.g. city, country), whether you tow heavy loads, and your performance preferences.

So let’s have a look at some of the pros and cons of diesel cars


Better fuel economy

Diesel vehicles tend to be more fuel efficient than comparable petrol vehicles. Diesel fuel contains more energy per unit of weight than petrol. That means that even though diesel tends to cost more than petrol it contains more potential energy, so less fuel is required to do the same amount of work. In fact, diesel engines can deliver up to 30% better fuel efficiency than similarly performing petrol engines.


More torque

Diesel engines produce significantly more torque than petrol engines. Torque is a measure of an engine’s rotational force. It determines the amount of work an engine can do, whereas horsepower refers to how quickly that work can be done. In layperson’s terms, torque is often referred to as “pulling power” or “grunt.” It’s the engine torque that gets the vehicle moving, which is why trucks, 4WDs and towing vehicles generally have diesel engines.

Due to the higher levels of torque, diesel vehicles generally deliver excellent acceleration and are much better for towing or carrying heavy loads than petrol vehicles.

More rugged and reliable

Diesel engines are designed to withstand higher compression forces than petrol engines. This means that they are generally more rugged and reliable. They are designed to last longer and will often command higher resale prices than petrol vehicles. That means that there are plenty of high-quality diesel engines for sale if you need a replacement engine. Additionally, diesel engines have fewer parts and don’t require tuning or spark plugs.


Less power

While diesel engines have higher torque than petrol engines they generally don’t rev as high, which means they have less horsepower. As a result, diesel engines don’t deliver the kinds of high performance that you’d get from a high-tuned petrol engine.

More expensive to buy and service

Diesel vehicles tend to be around 10-15% more expensive than petrol vehicles. And while they tend to require less servicing and repairs, they can also be more costly to service, requiring specialist mechanics and some higher prices for replacement parts. It’s worth factoring in these additional costs when deciding between petrol and diesel.

Diesel Engines

Higher emissions of nitrogen oxides

While diesel engines tend to emit less carbon dioxide than petrol engines, they emit significantly more toxic nitrogen dioxide and greenhouse gases greenhouse gas nitrous oxide and nitric oxide. In a petrol engine, a catalytic converter can be used to efficiently reduce the emissions of nitrogen oxides. Diesel engines, on the other hand, use particulate filters, which aren’t as efficient and can easily become clogged.

Ultimately, the choice between petrol and diesel comes down to which is going to suit you better. If you do a lot of towing or long-distance highway or country driving, then a diesel car might be right for you. However, if you’re mainly driving a small passenger car around the city, a petrol or petrol-hybrid car is probably the best choice.

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Steven Gostin

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