Drivers are being warned of petrol-price rip-offs around Australia, as some retailers fail to pass on savings to customers despite plummeting global oil prices.

Key points: Global oil prices have dropped, but that hasn't translated to all Australian bowsers

Global oil prices have dropped, but that hasn't translated to all Australian bowsers In Sydney's west, Retailers have been selling petrol for as low as 97 cents a litre

In Sydney's west, Retailers have been selling petrol for as low as 97 cents a litre However Canberra's petrol prices have dropped only about one per cent in the past three weeks

Over the past 24 hours, some retailers in Sydney's west have been selling regular unleaded fuel for as little as 96 cents a litre, but in other parts of the country, the prices remained more than 60 cents higher than that.

Global oil prices have been decreasing since December amid the COVID-19 outbreak, and a price war between large producers Saudi Arabia and Russia.

Melbourne-based independent investment expert Elio D'Amato said the price discrepancy at different petrol stations did not make sense.

"Last night I saw petrol prices that were at $1.55 or $1.60 [but] oil prices are at levels that we've not seen since around 2002," he said.

Prices have fallen below $1 a litres in some parts of Sydney. ( ABC News: Yudhana Sunartha )

Mr D'Amato said consumers had been lulled into believing a normal price for petrol was $1.50 per litre.

"There's this new margin that's been baked into petrol prices by retailers and, yes, we live in a consumer society where businesses have to make money. I get it," he said.

"But we've seen this big pullback in the oil price, and there hasn't been all that much evidence that it's actually making it to the price paid at the bowser."

Peter Khoury, from the National Roads and Motoring Association (NRMA), said the drop in oil prices had been reflected among Adelaide fuel retailers, with an average price of around $1.08 per litre across the city.

"That's what we want to start to see right across the country. We know what prices should be and they're way too high right now," Mr Khoury said.

Mr Khoury said petrol stations in other major capital cities including Brisbane, Melbourne and Perth were mostly charging around $1.30 per litre, with prices going up instead of down.

Canberra was one of the nation's worst-performing cities, he said, dropping around 1 per cent in the past three weeks.

This was "clearly not good enough", Mr Khoury said.

Mr D'Amato said Melbourne and Sydney were more competitive petrol markets where prices were often lower than regional areas.

"The Australian dollar is also around 57.7 US cents so that doesn't help oil prices here, given we import the majority of our oil into Australia and pay US dollars for it," he said.

"But even factoring that in, at such high prices, it doesn't add up."

Few locations in regional Australia are passing on the cut, with prices at Dubbo in the west of NSW lower than some capital cities, but still closer to $1.40 a litre.

"There is absolutely no reason why those service stations can't drop their price immediately, Mr Khoury said.

"We want to see those falls right across the country."

