Petrol prices are about to spike across Australia, and it has nothing to do with anything happening here

Petrol prices in Australia are about to climb, and the reason has nothing to do with anything happening on our side of the planet.

Brent crude hit a four month high this week, trading above $105 a barrel after a fresh wave of attacks on tankers and shipping routes in the Middle East. Houthi forces seized Yemen's port of Mocha, tanker attacks near the Strait of Hormuz have intensified, and hopes of a lasting peace deal between the US and Iran have stalled. Both major oil benchmarks are now trading above $100 a barrel for the first time in months.

Australia imports more than 90 per cent of the fuel it uses, and that fuel is priced in US dollars. When Brent crude rises this sharply, it flows through to the bowser here within weeks, exchange rate permitting. There is no local supply buffer standing between a conflict thousands of kilometres away and what you pay to fill up in Sydney or Perth.

This is the unglamorous side of a globalised fuel market. Petrol prices in Australia rarely move because of anything happening in Australia. They move because of decisions and conflicts in the Middle East, shipping routes through the Strait of Hormuz, and how nervous traders are feeling about supply on any given week.

It also means the usual advice, wait for the cheap part of the fuel cycle in your city, matters less than usual right now. Cycles are built around local competition between servos, not around a supply shock caused by tanker attacks on the other side of the world. This kind of price rise tends to move faster than any discounting cycle can offset.

For now, the advice is the boring but useful kind: fill up sooner rather than later if you are due, and expect prices to keep climbing while the situation in the Middle East remains unresolved. Nobody can say exactly how high or for how long, because that depends on decisions being made a long way from any Australian petrol station.

It is a reminder that even the most local, everyday costs are rarely actually local at all.