Petrol prices across Sydney have never been more expensive with many dreading filling up the tank.

9News can reveal what you can do to get the cheapest price at the petrol bowser.

Coles and Woolworths still offer four cent a litre discounts at participating service stations if you've spent $30 or more in the supermarket.

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NRMA members can save five cents a litre on premium fuel and three cents a litre on regular fuel at Ampol and Caltex service stations.

Loyalty card discounts are also available at 7-Eleven.

Prices can differ by up to 40 cents a litre on any given day, so checking the NRMA and NSW Government FuelCheck apps tell customers in real time where the cheapest petrol is.

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"Get access to that data, use it when you're filling up," NRMA spokesperson Peter Khoury said.

"That's the best way to save at the bowser and that's the best way to push back against these rising oil prices."