The Australian Government has reintroduced so-called 'dirty fuel' into the country to manage supply concerns, but the flow-on effects for engine function and vehicle warranties are causing consumer concern.
'Dirty fuel' refers to fuel that has a higher sulphur content, which in turn leads to higher levels of pollution and can cause car engines to deteriorate over time. Sulphur is a natural component of crude oil that is typically reduced or removed during the refining process.
In December 2025, Australia tightened its sulphur limits for unleaded petrol to less than 10 parts per million (ppm), bringing us into line with clean fuel standards in countries like the United States, United Kingdom and Japan.
However, we are currently seeing a return to pre-2025 fuel quality as the government temporarily relaxes these limits to mitigate fuel shortage concerns amid the conflict in the Middle East.
These relaxed limits will see 91 unleaded and premium 98 and 95 unleaded fuel sold with sulphur levels of up to 50 parts per million (ppm) for 60 days starting 15 March 2026.
While consumers have been urged not to worry, it is true that over time, high-sulphur petrol can affect a car's engine function, and newer cars are actually more susceptible to this than older cars.
“Modern vehicles are designed to run on low-sulphur fuel. Over time, high sulphur levels can impact emissions systems, fuel efficiency, and components like catalytic convertors and oxygen sensors,” Victorian Automotive Chamber of Commerce (VACC) CEO Peter Jones previously told Drive. “For the average driver, you’re unlikely to notice an immediate issue, but prolonged use isn’t ideal for vehicle performance or longevity. If you notice changes like reduced fuel efficiency, rough idling, or warning lights, it’s worth getting your vehicle checked."
Does dirty fuel affect your car's warranty?
Understandably, the use of dirty fuel has consumers worried not only for the functionality of their cars, but for the effect using this lower-quality fuel will have on their vehicle's warranty.
According to some of Australia's top-selling car brands, consumers shouldn't be too worried about the short-term use of high-sulphur fuel, but are encouraged to consult their manual and warranty terms and contact their dealer if they are concerned.
A Toyota Australia spokesperson said in a statement: "Regulatory adjustments to fuel and diesel specifications do not of themselves automatically affect vehicle warranty coverage. Current vehicles supplied by Toyota Australia are designed to operate safely on fuel with a sulphur content of up to 50ppm when used in accordance with the applicable owners’ manuals and normal operating conditions".
The Toyota spokesperson added that fuel and diesel that "meet the applicable Australian standards mandated at the time of use" would be deemed acceptable based on warranty eligibility standards.
The spokesperson said even newer vehicles optimised for fuel with lower sulphur levels – specifically those sold after the introduction of stricter Euro 6 tailpipe emissions standards in December 2025 – could tolerate 'dirty fuel' for a "limited period".
"While EURO 6 vehicles are optimised for 10ppm sulphur fuel, they are expected to tolerate higher sulphur levels for limited periods, including up to six months, without inherent issue," the spokesperson said.
However, while a Ford Australia spokesperson said that "all Ford vehicles sold in Australia have been designed to operate on the Australian minimum fuel standards", they urged customers to "review their manual and warranty terms for guidance on approved fuel standards".
"While Ford vehicles are designed to tolerate variations within regulated fuel standards, Ford recommends customers use fuel that meets the specifications outlined in their owner’s manual to ensure optimal performance, efficiency and longevity," the spokesperson said.
A Mazda Australia spokesperson also reassured customers the relaxed fuel standards were not expected to impact the warranties of Mazda cars.
"[The relaxed petrol sulphur limits] align to the specification of fuel that was available pre-December 2025, and we don't envisage any adverse effects or issues related to this that would impact the vehicle warranty," they said in a statement.
"Mazda Australia would advise customers to continue driving their cars and filling up as normal. Owners can also check their owner’s manual for the fuel requirements of their vehicle if in doubt."
On the off chance you find your car's function altered by the change in fuel, you can take a few steps to safeguard yourself.
According to Consumer Affairs Victoria, consumers who suspect their vehicle has been damaged by contaminated fuel should send a formal letter to the retailer to report contamination, seek written confirmation from a mechanic, contact their insurer and report fuel contamination to the Department of Climate Change, Energy, the Environment and Water (DCCEEW).
Susannah Guthrie has been a journalist for over a decade, covering everything from world news to fashion, entertainment, health and now cars. Having previously worked across titles like The New Daily, Elle, Harper's Bazaar, People Magazine and Cosmopolitan, Susannah now relishes testing family cars with the help of her husband and three-year-old son.
