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Here's a sneaky way to pay 30c less for petrol

Image: AAP Images

Fluctuating petrol prices have a big impact on Australian wallets, with so much of the population still overwhelmingly car-dependent.

Even people who commute to work using public transport during the working week will hop in the car on weekends for children's appointments, social activities and leisure trips.

However, petrol retailers have a price cycle that keeps motorists guessing as to when fuel will be at its cheapest. In Sydney, for example, this cycle can be anywhere from 25 to 60 days from peak to peak.

And this cycle can have a massive bearing on how much you pay for the same amount of fuel. The price per litre in Sydney can vary by as much as 30 cents.

But there is a way you can beat the cycle and buy petrol for cheap when everyone else is paying top dollar.

Fuel retailer 7-Eleven has a mobile app that allows Australians to lock in the petrol price when it's cheap. When you fill up later, you can pay that price.

The catch is that you have to use the frozen price within seven days of locking it in. So if you time it so that the price is locked just at the end of the cheap period, you could be paying as much as 30 cents less per litre one week later when prices have peaked.

In order to lock in lower prices, you need to put some credit into the 7-Eleven account. For example, if you deposit $40 into your account, you will be able to lock in $40 worth of petrol.

But there is no obligation to pay for your petrol at the service station using that credit. You can pay for your fuel by all the usual means – cash, credit card, debit card – so you can keep the credit in as long as you want to use the 7-Eleven app.

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