Is premium diesel worth it?

9 August 2024

No one likes spending more money on fuel than they need to, which is why you probably shouldn’t waste your money on pumping premium diesel into your tank.

Fuel companies market premium diesel as containing additives, which they claim can help to clean your vehicle’s engine, inhibit rust and improve performance.

While independent testing has indicated these fuels do contain additives over and above other diesel fuels, whether there are any benefits provided by these additives is unknown.

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Far more obvious is the price difference between premium diesel fuel and regular diesel. By creating some differentiation between regular and premium diesel, fuel companies also create an opportunity to charge more for the product that is perceived to be better.

All diesel fuel sold in Australia must meet the same standards, which includes a low sulphur content of no more than 10 parts per million (PPM).

The cetane rating of regular and premium diesel, which is a measure of how quickly and efficiently it burns, is the same for regular and premium. This means there are no performance benefits to using premium diesel.

So the only differences are the additives, which at this stage are not independently proven to be beneficial, and of course the price.

On the other hand, premium petrol with the higher octane ratings of 95 and 98 RON, may produce some small improvements in performance and fuel economy, if used in a vehicle that’s recommended to run on 91 RON. In most cases though, any gains in fuel economy are typically offset by the higher cost of premium petrol.

Diesel fuel regulations

Fuel standards are set and regulated by the Australian Government. For diesel, the Fuel Quality Standards (Automotive Diesel) Determination 2019 sets out the specifications for all diesel fuel sold here.

Those standards, according to the Department of Climate, Energy, the Environment and Water, are in place to reduce fuel pollutants, facilitate improved engine and emissions control technologies developed by industry, and improve engine operation.

Fuel companies’ claims about the benefits of the additives they use in premium diesel are difficult to ascertain, as they provide sketchy details about them and there is little independent research to back their claims.

Ampol claims it’s Amplify Premium Diesel has “unique, advanced additives” that will “restore and maintain fuel injector cleanliness.” They say that with regular use it will “protect your engine and provide up to 100% power restoration.” They also add a caveat that the results may vary “depending on the engine, environmental conditions and other factors.”

Similarly, Shell states it’s V-Power diesel “removes fuel system deposits and helps restore lost performance.”

In 2018, independent laboratory testing commissioned by RAC of diesel fuels from various fuel outlets across Perth found all samples were within the specifications required.

And if you’re wondering about truck diesel, it’s also exactly the same stuff. The only difference is that the nozzle on the pump is bigger, so it probably won’t fit the fuel tank of a passenger vehicle, and the rate at which the fuel flows from the nozzle is higher.