Australia's Sulphur Setback: What Higher-Sulphur Fuel Means for Your Engine

In December 2025, Australia finally caught up with the rest of the developed world, capping sulphur in petrol at just 10 parts per million (ppm) — down from 150 ppm in regular 91 RON and 50 ppm in premium grades. Now, just three months later, the Federal Government is reversing course. With the Strait of Hormuz effectively closed following US–Israeli military strikes on Iran, Australia’s already-precarious fuel supply chain is under severe pressure. The response? A 60-day emergency exemption allowing sulphur levels to rise to 50 ppm across all petrol grades, running until 31 May 2026. It’s a pragmatic call in a genuine crisis — but it’s worth understanding what sulphur actually does inside your engine.

The Engine Impacts of Higher Sulphur

Sulphur is a natural constituent of crude oil. When burnt, it forms sulphur dioxide which, in the presence of moisture in the combustion chamber, converts to sulphurous and sulphuric acid. These acids are the real problem. They attack engine internals — cylinder walls, piston rings, valve stems and bearing surfaces — accelerating corrosive wear. Modern engines with catalytic converters and diesel particulate filters (DPFs) are especially vulnerable: sulphur poisons the precious metal catalysts and clogs filter substrates, reducing efficiency and potentially triggering expensive repairs. Engines equipped with petrol particulate filters (PPFs) — increasingly common on Euro 6d vehicles — face similar risks. Higher sulphur also degrades engine oil more rapidly. It reacts with the oil’s alkaline additives — the Total Base Number (TBN) reserve — neutralising the very compounds designed to protect your engine between oil changes. The result is faster oil acidification, increased sludge formation, and reduced lubricant film strength.

What You Can Do Right Now

The good news: for the vast majority of Australian vehicles — particularly those built before December 2025 — the temporary 50 ppm fuel is nothing new. Your engine has been running on it for years. That said, there are sensible precautions worth taking during this exemption period:

•        Use a premium full-synthetic engine oil with a high TBN rating. A robust alkaline reserve offers greater resistance to acid-induced degradation. BOALA’s HOCL and LubeAlloy ranges are formulated for exactly this kind of extended-protection duty.

•        Consider shortening your oil change interval slightly during the 60-day window, particularly if your vehicle sees hard or high-load use.

•        Owners of vehicles with PPFs or DPFs should follow manufacturer guidance carefully and consider using the highest-grade fuel available.

•        Keep an eye on your fuel-trim and emissions warning lights. If your vehicle flags catalyst or filter issues during this period, sulphur exposure may be a contributing factor.

The 10 ppm standard returns on 1 September 2026 — and not a moment too soon. In the meantime, the right oil is your engine’s best friend.