Road User Charge (RUC)

RUC costs apply to all vehicles over 3.5 tonnes and cars using fuel that isn’t taxed at source, such as diesel. For vehicles with a Mass Gross Weight of up to 2 tonnes, RUC costs $36.07 per 1000 km, so this needs to be considered as a direct additional cost of diesel.

Registration Costs

The annual registration fee is a cost that is fixed regardless of distance travelled. This is where higher mileage vehicles have an advantage over low mileage vehicles. The annual registration fee for a private car is currently $211.84 for petrol and $336.69 for diesel, a difference of $124.85.

Service and maintenance costs

Diesel vehicles have traditionally been more expensive to service. However, many modern diesels now have much longer service intervals – up to 40,000km or 2 years in some instances. Fuel filters are usually a recommended service item so this is a cost to be considered. However, service intervals depend on the manufacturer’s recommendation, so different makes and models will vary.

Convenience

Historically, diesel pumps were tucked away in the corner of the service station. This is usually no longer the case although may still be evident in remote areas. Ensuring the RUC is up to date is another potential inconvenience of operating a diesel vehicle. However, the biggest convenience of operating a diesel vehicle is it requires re-fuelling less often.

Noise and performance

Older diesel engines tend to be very noisy; however modern technology has greatly improved noise levels. Performance used to be poor for diesel vehicles, modern direct injection, turbo intercooled diesel engines means this is no longer an issue.

Environmental impact

Neither petrol nor diesel engines are good for the environment. However, minimising environmental damage should be of concern to all motorists.

  • CO2 (Carbon dioxide) is one of the major greenhouse gases that has been linked to discussions on climate change. Generally, diesel engines emit a lower level of CO2 per kilometre travelled so could be considered better for the environment.
  • CO (Carbon monoxide) is a lethal gas produced by petrol engines. While CO emissions have been combated with the use of catalytic convertors, they only work effectively once they have reached operating temperature, so CO is still a by-product of petrol engines during the warm-up phase.
  • NOx (Nitrous Oxide) combines with low level ozone to form smog. While NOx can be higher in a new diesel than a new petrol engine, petrol engines produce more NOx over time.
  • HC (Hydrocarbon) in fuels contains harmful chemicals including benzene. Benzene has been proved to be highly carcinogenic. HC emissions are much higher in petrol engines than diesel.
  • SPM (Suspended Particulate Matter) refers to particles suspended in the air, such as soot, emitted from the exhaust of a diesel engine. While modern diesels are fitted with particulate filters, SPM emissions are still high in older diesel engines.

To summarise the environmental impact of petrol vs diesel engines: Diesel comes out on top with regards to CO2, CO and HC. Both are around the same when it comes to NOx and diesel is worse for SPM.

Generally speaking, a large 4WD vehicle doing high mileage would be better off diesel powered and a small hatchback, doing a low mileage may be better being petrol powered.

However, there are many factors to consider, and each factor needs to be considered in conjunction with the others. Ultimately, it comes down to the individual motorist’s decision as to which fuel best serves their purpose.