Driving tests

Should you buy a petrol or diesel car?

If you are choosing a new car or your first car your main choices (unless you really want to go all-electric) are petrol (including petrol-hybrid) or diesel. Let’s assume you’re not heading down the hybrid route at the moment and look at cars solely powered by petrol or diesel.

Diesel is cheaper to buy, but you have to pay road user charges per kilometer. This makes costs for freight vehicles slightly more predictable as it’s easier to work out a proportion of the costs as a distance rather than by fuel economy which can vary depending on the terrain, traffic, type of vehicle, etc.

But looking at cars and SUVs, we find the following:

The servicing costs for petrol and diesel cars are roughly the same, but components for diesel engines are more pricey. Diesel engines are (generally) less reliable than petrol engines, therefore over the lifetime of the engine the diesel motor will probably cost you more in maintenance.

It’s more expensive to register a diesel vehicle

Registration of motor vehicle (issued with standard plates, and includes your first vehicle licence) 6 months 12 months
Passenger car/van
Private passenger Petrol driven – 1301-2600cc 291.08 431.25
Petrol driven – 2601-4000cc 322.13 462.30
Non-petrol driven – 1301-2600cc 361.77 572.64
Non-petrol driven – 2601-4000cc 392.82 603.69

And when you go to pay for your licence, it’s more expensive every year.

Motor vehicle type/usage 3 months 6 months 12 months
Passenger car
Petrol driven – private 70.30 140.38 280.55
Non-petrol driven – private 105.66 211.07 421.94

A diesel vehicle usually has much more torque than the equivalent petrol vehicle and this makes them superior for towing. If you want to tow a caravan, boat or trailer, a diesel vehicle will usually give you the best option unless you are opting for a petrol car with a large displacement motor.

Because diesel engines have more torque and superior fuel economy, they are often better for large SUVs.

Diesel engines (particularly older ones) can be quite noisy in comparison to petrol engines. Modern diesel cars are quiet on the inside due to much improve sound deadening, but will still be more noisy on the outside.

Diesel cars tend to be more expensive than their petrol equivalents because diesel motors are more expensive. On larger vehicles the percentage isn’t so much because the cost of the motor is less in relation to the whole car, but in a smaller car, manufacturers tend to go with smaller displacement engines, often with turbocharging, supercharging or both to make up for lost torque.

Diesel engines produce less CO2 but more particulates. If the car has a diesel particulate filter fitted it can mean that the engine is a very clean option, but these filters can get clogged over time and are expensive to replace.

If you are considering a diesel because your main motivation is saving money, check out our guide to driving more economically first. Many people waste up to a third more fuel than they need to by using poor driving techniques.

Advantages of buying a petrol-powered car

  • Usually cheaper buy and to run if you do less kilometers
  • Usually quieter and more refined, although this is less of an issue with modern diesels
  • Usually more reliable and cheaper to maintain
  • Usually a better option in a smaller car

Advantages of buying a diesel-powered car

  • Usually better for towing
  • Fuel economy is superior
  • Usually cheaper to run if you do more kilometers
  • Often hold their resale value better
  • Produce less pollution if fitted with a diesel particulate filter.

However, with the rapid advances in hybrid technology, diesel’s economy advantage has been cut dramatically.

 

 

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Darren is a member of the Institute of Advanced Motorists and the NZ Motoring Writers' Guild

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Posted in Advice, Car
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