Feature article
Diesel vs Petrol Vehicles in NZ
The combustion engine continues to power the bulk of the vehicles in New Zealand, fueled by petrol or diesel.
Last updated: 11 September 2024
The internal combustion engine continues to power the bulk of the vehicle fleet in New Zealand. And it’s either fueled by petrol or diesel. When it comes to the diesel vs petrol debate, the answer really depends on what type of vehicle you are talking about, and what sort of job you are wanting it to do.
Diesel vs Petrol, what’s the difference?
While the two are quite similar, there are many differences too. Like how each one combusts its fuel to make power. Diesels use compression ignition, igniting the fuel under pressure to create the bang, while a petrol engine uses spark ignition (so a diesel engine has no spark plugs) to ignite the gas to make the bang which makes the power.
Generally speaking, petrol engines make more power as they can rev higher and faster, while diesels make more torque (think of it as pulling power). Petrol engines tend to be quieter in operation, diesels emitting the odd rattle, though modern units are fairly refined in this regard.
The low end torque of a diesel makes them easy to drive, and so you don’t need to rev them as high to accelerate. This helps return good fuel efficiency. Also helping in this regard, the diesel combustion process is more efficient. And there is more energy in a litre of diesel than there is a litre of petrol. And so, diesels generally return better fuel economy. However, in the past decade, petrol engine technology such as direct injection and low pressure turbocharging (both of which diesel engines use) has bridged that gap. And so turbopetrols can make comparable torque while still producing more power. The fuel consumption disparity is also much narrower than it used to be.
Diesel engines are more expensive to build (the pressure of the ignition process means components need to be more robust, therefore adding cost) so the diesel variant of a model usually comes with a premium. And now they require more filters and convertors on the exhaust side to meet stricter emissions standards, making them even more expensive. Diesels produce more particulate matter and gases like NOx (Nitrous Oxide) which are harmful to human health. Petrol engines still generate emissions that are harmful to both humans and the environment too however.
Diesel on the outer
European manufacturers were big producers of diesel-powered cars, but things have changed recently. For instance you can no longer get a diesel-powered 3 Series, Golf, C-Class, or even larger models like the 5 Series and E-Class new in NZ. Events such as VW’s Dieselgate affair, where the company was caught cheating on emissions tests, didn’t help the diesel cause. Also, it is more expensive to develop diesel engine technology that meets stricter emissions standards, further driving up costs.
Diesels tend to require more frequent servicing and generally it is more expensive to service a diesel engine compared with a petrol engine of a comparative size.
While superior fuel economy has traditionally been a diesel pro, modern petrol electric hybrids are a better option now, especially for urban motorists. And there are no Road User Charges to worry with those either.
Does diesel still have a place?
Diesel still has its place in some sectors of the car market, and that is the large SUV and commercial vehicles like vans and utes. The low end torque that a diesel makes is more suited to these applications where it is advantageous when towing or venturing off road.
So in summary, when considering passenger vehicles like cars and small and medium SUVs, you’re better to go for petrol or hybrid power. But for large SUVs, 4x4s, double cab utes and vans, the diesel still reigns supreme.
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