Preparing to buy – the basics to know about car engines

October 4, 2018 5:25 am |,

If cars aren't your thing, walking into a sales yard looking for your next one can be a daunting prospect. When your sales person starts talking about how the 2018 Kia Optima has a great four-cylinder engine with 180 horsepower, it's easy to become quickly overwhelmed.

Which is why we've created this simple guide to car engines, so you can nod along knowledgeably, and feel confident that you aren't going in blind.

Basic Terminology

When it comes to terms bandied about in car engine conversations, there are four main ones that are useful to learn. While you can break it down further should you choose to, understanding what these four mean will set you up with a basic understanding of what you'll need to know when buying a new car.


Measured in kilowatts, horsepower tells you how much power the engine produces, and is an indicator of the running capacity of your car. 

Horsepower is measured and reported at the vehicle's optimal engine speed – at different revolutions per minute (RPMs) the output will be less.

A car that has about 300 kilowatts of horsepower is more than enough for a road car, while having enough kick for a touch of speed when needed. 


The total volume of all the cylinders in an engine is described as the displacement, and is stated in litres. When a car is described as a 2.0 litre engine, this is referring to the space taken up underneath the hood by all the cylinders.

Generally, the larger the engine, the more horsepower is produced.


Cylinders are where the oomph of a car is created. Inside them, gasoline is ignited and burned to generate horsepower which is then delivered the rest of the vehicle.

Though other combinations are available, most cars and SUVs contain either four, six, or eight cylinders.


Related to horsepower, this term is probably the trickiest one to understand. Torque is the pulling or turning power of an engine, and is measured in newton metres (Nm). That feeling when you start driving, and you get pressed back into the seat, is torque in action.

The larger the vehicle involved, the more important torque is to manage the extra weight. For small city cars, minimal torque is necessary for you to whiz around town. However, when it comes to a bigger SUV, or a vehicle that's used to tow trailers, it will take more to get them moving.

Like horsepower, the torque measurement is taken at a certain engine speed, and the output changes depending on what RPM the car is sitting at.

Petrol vs. Diesel

With the basic terminology sorted, it's time to consider the the two main engine types you need to consider when buying a road car. With diesels becoming more popular due to improvements in performance, what you want your car for is now the main deciding factor.


More efficient with fuel usage, diesel engines are good for long-distance travelling. Their peak torque performance hits at a lower engine speed, which makes them good for overtaking and towing heavy loads.

The downfall is that the emissions they produce aren't very environmentally friendly, and initial purchasing costs, as well as servicing fees, tend to be more expensive.


An engine running on petrol is usually a more quiet affair than when diesel is involved.

An engine running on petrol is usually a quieter affair than when diesel is involved. They reach peak performance for horsepower and torque at higher RPMs. This tends to make them more engaging, and to have more grunt at higher speeds, which is why petrol is used in many different types of race cars. 

Engines using petrol are also generally better for the environment, and require less maintenance to keep them performing well.

Fuel efficiency is where a petrol engine tends to let you down however, so be aware of this when deciding what you want your car for.

Now that you have a basic understanding of a car engine, head down to the Macarthur Kia dealership and know exactly what it means when the Optima is described as having a 2.4L petrol engine.