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Q. The government has said that fuel retailers are going to sell petrol containing more sulfur to help extend Australian fuel supplies. Is that fuel bad for my engine?
A.It was only from December 2025 that the Australian Government mandated that all grades of petrol in Australia were to be limited to a maximum sulfur content of 10 parts per million (ppm). This is called the New Vehicle Efficiency Standard. Prior to that, 91 RON fuel sold in Australia had an allowable sulfur content of up to 150ppm. Premium fuels (95 and 98 RON) were allowed to contain up to 50ppm sulfur up to December 2025.
What the government has done now is temporarily revert to a 50ppm allowable sulphur content for 91, 95 and 98 RON fuels. For 91, this is still much lower than the previous 150ppm limit and the same as the previous 50ppm limits for premium petrol grades. In short, these temporary changes will have no impact on your car’s engine. And remember, these are upper limits – prior testing by RAC has indicated most fuels tested contained considerably lower sulfur than the upper limit allowed.
Q. The government is talking about introducing a lower grade diesel fuel and has openly stated that this will have no effect on our vehicle’s engines. Is that true?
A. Lowering the diesel flashpoint slightly, such as from 61.5°C to 60.5°C as stated in the release from the Department of Climate Change, Energy, the Environment and Water, is unlikely to have any impact on modern engine performance, fuel efficiency, or emissions.
Q. My car takes 95 RON fuel. Can I use 91 in it for a short time to save money?
A. No. Using petrol that is a lower octane number than the one recommended for your car can cause engine damage and void your car’s warranty. The RON, which stands for Research Octane Number, indicates the fuel’s anti-knock threshold. When you use 91RON fuel in a 95 or 98 RON car, you may hear a ‘knocking’ or pinging sound when the engine is under load. This is the petrol detonating uncontrollably rather than burning at the right time in the right way. Choosing fuel with a lower octane number than the one your car should use may save you some money in the short term, but it’ll cost you much more down the road.
Q. Can I use E10 fuel in my car and will it save me money?
A. E10 has limited availability in WA, but if you do find it and want to use it, make sure its octane rating (usually 94 RON) is high enough for your vehicle. For example, if your vehicle requires 95 RON or above, we’d recommend sticking with that. E10 is likely to only save you money if it is cheaper than 91, because the slightly lower energy density of E10 means your car will need more of it.
