Millions of Australian motorists could be slugged with higher petrol costs over the next two weeks after global oil prices hit a two-year high.

The price of Brent Crude, a global benchmark for oil prices, climbed 5 per cent last week to reach its highest level since May 2019.

The sharp rise was driven by growing economic optimism in the US and economists said it could lead to a 3.5 per cent increase in Australian petrol prices, which roughly equates to an extra $2.50 per tank.

“If global prices are maintained at current levels, pump prices may lift around 5 cents a litre over the next fortnight,” CommSec chief economist Craig James told The New Daily.

That would take the average national retail price from 143.5 cents to 148.5 cents, based on the latest weekly data from the Australian Institute of Petroleum.

Mr James said if prices crept much higher than that, households would look to cut back on spending.

“If prices are maintained near $1.50 to $1.60 a litre they will serve to restrain consumer spending,” the economist warned.

NRMA spokesman Peter Khoury also said prices would rise but noted the strength of the Australian dollar would minimise the size of the hikes as oil was traded in US dollars.

As ever, the message for consumers is to shop around and pay close attention to retailers’ pricing cycles.

Past research from the ACCC found that motorists who fill up a 50-litre tank once a week could save between $150 and $520 a year by buying at the bottom of pricing cycles and about $350 a year by avoiding big-name brands.

The ACCC provides a state-by-state breakdown of retail pricing cycles on its website and services like MotorMouth and Compare the Market can help motorists seek out the lowest possible prices.

According to the ACCC’s website on Monday:

• Sydney and Melbourne motorists “should delay buying petrol” as prices in the two biggest cities are on the way down
• Brisbane motorists should “shop around”, as although prices are rising some retailers have not increased prices yet
• In Adelaide, now is a “good time for motorists to buy petrol” as prices appear to be at the lowest point of the cycle
• People in Perth who want to save money should always fill up their tanks on Tuesday, when prices hit their weekly low.