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Petrol, diesel or LPG?

Petrol, diesel or LPG?

When you’re choosing a new vehicle, it can seem like there are endless options to navigate through. One thing to factor into your decision making is the pros and cons of buying a car powered by petrol, diesel or LPG. Generally, a large vehicle doing high mileage would benefit from being diesel powered, while a small car is more economical if it’s petrol or LPG powered. But there are many factors to consider – not just price – and not always one right answer.

The New Zealand Automobile Association identifies the following points to consider when deciding whether diesel, petrol or LPG is the right choice for you. 

How far will the vehicle travel?

Diesel may be the cheaper option if you travel a large number of kilometres per year. Alternatively, if you travel 15,000km or less per year, petrol or LPG may be the best option for you.

The size and type of vehicle

SUVs and other large cars have higher fuel consumption – and so diesel power is often best. Small petrol or LPG cars (less than 1.6 L) will likely be very efficient.

Fuel economy

According to the AA (Automobile Association), diesel cars usually travel up to 30 per cent further on a tank of fuel. 

Purchase price

Traditionally diesel vehicles have been significantly more expensive to buy than petrol cars. Alternatively, converting your petrol car to LPG can be expensive – something to consider when choosing LPG as an option. Remember that while you have little control over the eventual running costs, you may be able to negotiate the purchase price of your vehicle. 


Petrol models of large 4WD vehicles often depreciate faster than the diesel models.

Fuel price

Diesel remains cheaper at the pump, despite rises in all fuel prices. Road user charges (RUC) and higher registration charges need to be considered also. LPG can be up to 60 per cent cheaper than petrol, litre for litre.

Road User Charges

RUC applies to:

  • All cars, such as those running on diesel, that are not taxed at source
  • All vehicles over 3.5 tonnes – regardless of fuel type

Registration costs

This fee is fixed – regardless of the distance travelled. Costs can vary depending on vehicle class, designation and fuel type.

Service and maintenance costs

Traditionally, diesel vehicles have been more costly to service. Now the difference may be less, as modern diesel-powered vehicles don’t require servicing as often as in the past – though this depends on the manufacturer’s recommendations. Note that LPG engines have a potentially longer engine life.

Noise and performance

Older diesel engines tend to be noisier, but this isn’t such an issue with modern vehicles. Modern common rail diesel engines need clean fuel, so refuelling at busy stations is advised – the higher turnover means the fuel isn’t sitting around for long. By contrast, refuelling from a diesel tank on a farm is not advised. Generally, LPG engines are not as powerful as petrol or diesel.

Environmental impact

No engines are good for the environment. Both diesel and petrol powered vehicles emit a range of pollutants. Arguably, a diesel vehicle causes less pollution than its petrol equivalent. However, LPG engines have reduced exhaust emissions in comparison to petrol and diesel.

Car yard discounts and resale

Discounts at the car yard on both diesel and petrol powered vehicles are common, and it’s cheaper to buy an ex-demonstrator model. Service plans are also becoming more common, and are often factored into the initial price – something else to consider. Resale prices can also favour diesel, petrol or LPG, depending on where the market demand is.

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