Petrol prices have continued to tumble with unleaded 91 down more than 20c a litre on just a week ago - the price drop giving much-needed relief for motorists.

If you fill up today at Gull Speedlane in Wiri, unleaded 91 will cost you $2.58 per litre. A week ago it was $2.67 and was the lowest in the country.

Today, at the time of publication, the cheapest in Auckland was Mobil Cavendish Drive in Papatoetoe with unleaded 91 for $2.56 per litre.

In Christchurch, Waitomo Fitzgerald had unleaded 91 advertised for $2.53 per litre.

Even at the most expensive place to fill your tank - GAS Kaurilands in Titirangi - unleaded 91 has dipped just below the $3 mark at $2.99 according to the Gaspy app.

A week ago it was $3.31 a litre - a price drop of more than 30c in a week.

The relief at the pump comes as petrol costs drop overseas and Energy Minister Megan Woods asked petrol companies to cut their fuel margins. Despite the drop, margins are still at a historical high.

The Gaspy app helps motorists find the cheapest fuel near them. Photo / Supplied

Greig Epps from MTA said the price drop was good news at a time when supply chain issues and increased transport costs were high.

He said often smaller petrol stations were blamed for high prices but these had been set well before.

"The petrol stations often cop the flack for prices when actually by the time it gets to the pump all the pricing has been done," he said.

"The wholesale market is what needs to be looked at and minister [Woods] is following up on what the Commerce Commission has said - keep an eye on the importers and the wholesale middle market.

"Some pressure in that space should translate to some better pricing at the pumps."

This week's lower prices come after a year of steadily climbing petrol costs.

In March Finance Minister Grant Robertson and Energy Minister Megan Woods announced a short-term cut in petrol excise duty. This has just been extended until the end of January.

The cut reduced the cost of filling a 40-litre tank of petrol by more than $11, Robertson said.

The petrol price drop comes at a time New Zealanders face a cost of living crisis.

A new study by not-for-profit organisations Orange Sky and conducted by YouGov revealed many New Zealanders were facing hardship and struggled to pay bills and buy essential items like petrol and food.

The study found one in four Kiwis struggled to make ends meet at least once a month with some fearing they would lose their home, as inflation hits 7.3 per cent.

MTA's top fuel-saving tips

Use an app: Find the best price nearby through an app like Gaspy.

Get the discount: It's free to sign up for petrol discount cards, do it and save 6c off per litre.

Service and tune your vehicle: Regular services and tune-ups could reduce your fuel consumption by up to 4 per cent.

Drive smoothly: Avoid harsh acceleration and braking as this can save up to 20 per cent on your fuel use.

Properly inflate your tyres: Under-inflated tyres are a significant contributor to increased fuel consumption.

Fill it up: When filling up, stop at the first click – if you continue beyond this, you risk overflowing the tank and wasting fuel.

Avoid prolonged idling: Modern vehicles are designed to operate efficiently from start up and don't need to be "warmed up".