Should I buy a petrol or diesel car?

The push to lower passenger car emissions in Australia began in earnest in 2025 with the introduction of the New Vehicle Efficiency Standard (NVES).

But even so, a perennial debate rages on: should I buy petrol or diesel? Even with the advent of hybrid, plug-in hybrid, electric and even hydrogen technologies in Australia, the reality is that new petrol and diesel cars remain the predominant choice for most Aussies. And furthermore, there’s still plenty of shelf life in them yet.

To help wade through all the confusion, we've put together a comparison of diesel and petrol cars, which covers factors including environment, running costs and intended use.

Let’s begin with the oil burners.

Pros of buying a diesel car

Although diesels aren’t as popular as they once were in Australia – partly because of less availability coming out of Europe and Asia, with more carmakers prioritising petrol drivetrains – the truth is they still have plenty of merit.

1. To begin with, diesels are more fuel efficient than petrol engines and emit less CO2. This is because diesel as a fuel source contains more carbon than petrol, and the engine design makes them more efficient at burning it.
   
   The immediate counterpoint to the ‘less CO2’ rule is that diesel engines produce more harmful pollutants like nitrogen oxides (NOx), so any argument that diesels are in fact ‘cleaner’ than petrol should be kept within this context.
2. Diesels produce considerably more torque (pulling power) than their petrol counterparts, which makes them good engines for towing or carrying heavy loads – eg: seven occupants – on a regular basis.
3. Due to diesel engines' increased fuel economy, you can generally get more kilometres out of a tank, meaning less trips to the service station. This is changing, however, with the advent of more advanced petrol engines.
4. Diesel fuel is less prone to price fluctuations than petrol.
5. Some diesel vehicles are even more economical than hybrids and are cheaper to buy.
6. Diesel engines are generally more rugged than petrol engines, as they have to withstand higher compression ratios; this means better longevity. Mercedes-Benz holds the longevity record, with several vehicles clocking more than 900,000 miles (1.45 million kilometres!) on their original engine. Due to their perceived 'toughness', resale values are usually better for diesels than their petrol equivalents.
7. Diesel engines don't have as many parts as petrol engines. They don't require tuning or sparkplugs.
8. Diesels are great on the highway, as they provide strong overtaking power and can often do so without changing down gears

Pros of buying a petrol car

Even as recently as 20 years ago, the petrol engine was overlooked by many in favour of diesel, because it struggled to match the efficiency and pulling power.

However, with the advent of direct injection, turbocharging and variable compression ratios, the humble petrol is now much more versatile. And, with the advent of synthetic fuels, the petrol stands to be around for decades to come.

Here is why petrol is considered the better fuel source by many:

1. Regular unleaded fuel is cheaper at the pump than diesel. There is also a wider availability of petrol types to best suit the style of car and driving, from 91 ethanol-blended octane through to 98 octane.
2. Petrol models can be anywhere from 10-15 per cent cheaper than their diesel counterparts at the point of sale. It is important to work out how many years it will take to recoup the initial outlay (depending on the price of fuel and the kilometres you are driving).
3. Petrol engines are generally cheaper to service, with diesel fuel system components often costing many times more than the equivalent part for a petrol engine.
4. Although petrol particulate filters have begun creeping into new petrol engines, they aren’t required to remove the nasty nitrogen dioxide particles from polluting the atmosphere, like diesel. These can become clogged when used for mainly urban driving which can lead to harmful gases polluting the atmosphere. A DPF is also expensive to replace, running up to $8000 for some models!
5. Used diesel cars, unless properly serviced and maintained, can attract much higher repair costs than used petrol cars.
6. Petrol engines are much better suited to the stop-start nature of commuting, and are a better fit if you’re not regularly traveling open road miles.
7. While diesel engines are getting quieter, they don’t offer the same muted idle and refined sound as a petrol through the rev range. Even in 2025, many still sound like trucks.
8. Many service stations have a greater bowser availability of petrol pumps, meaning you won’t have to venture out to uncovered, remote pumps.
9. There is a greater choice of petrol cars in the market, and petrol engines are more prevalent in a hybrid drivetrain and plug-in hybrid drivetrains (which combine a combustion engine with an electric motor for greater efficiency) due to their ability to intermittently stop-start on command.

Verdict - petrol or diesel?

Newer diesel vehicles contain particulate filters that are supposed to catch the nasty particles of nitrogen dioxide which has been linked to cardiovascular and respiratory disease.

A 2018 report by The World Health Organisation stated ambient (outdoor) air pollution in both city and country areas causes up to 4.2 million premature deaths worldwide each year. Be sure to check your car's figures (if buying new) and the condition of the filter (if buying used).

When you look at the pros and cons of buying a diesel or petrol car, there's no simple way to determine which is better as it really depends on your personal circumstance and how you plan to use the vehicle. There are however, a few things to consider.

• If you have a large family and will be transporting heavy loads or potentially towing a trailer, small caravan etc. often, then a diesel is the pick.
• If, however, you're wanting a small runabout or car to travel around the urban environment, then petrol could be a better bet – especially one with hybrid availability.
• Whichever car you drive, make sure you download the My NRMA app so you can keep an eye on the cheapest diesel and best diesel prices in your area. Plus, you can save up to 5 cents per litre on fuels and can stack their NRMA rewards with Everyday Rewards and in store discounts to save up to 13 cents per litre at participating Ampol service stations.