Two big chains have reduced what motorists pay at the pump after an oil price plunge.

Oil prices plunged as much as 30 per cent as markets opened this morning.

AA says motorists are paying up to 40 cents more at the pump for premium petrol.

Mark Stockdale says the AA expects fuel prices to fall at pumps around the country.

The cheap prices won't last for long - from 7am Thursday until midday Friday.

Crude prices dropped 6 per cent as Saudi Arabia said repairs would take only three weeks.

Economist Cameron Bagrie warned prices could reach $3 a litre in a worst-case scenario.

Great Barrier residents are still paying for $3 upwards, per litre, for petrol.

The PM is vowing to act, but how far can the Government drive down fuel prices?

Kiwis will have a smile on their fuel dial with this deal!

Fuel frenzy: Two BP stations give away free petrol. Video / Supplied

More official interest rate cuts are in store despite an expected lift in the quarter CPI.

Fuel prices aren't budging in the central city a week on from Waitomo opening.

The highest price in Wellington today was $2.35 for 91.

Low costs at the new fuel stop shouldn't be seen as a good thing, Iona Pannett says.

Gull is gearing up to open service stations in the South Island.

The national carrier has launched $19 one-way fares on its Grabaseat platform.

The City of Sails has not seen prices this low since June.

Government has begun the official process of investigating the petrol industry.

The Commence Minister said the market regulator is "no stranger to pressure"

From 7am today until midday tomorrow, fuel pumps at Gull around the nation will be busy.

Spending on back office, marketing and work travel will be cut, and more savings likely.

Kiwi drivers can now rejoice as Waitomo pumps are dropping its fuel prices to $2 a litre.

Rising oil prices this year have knocked airline shares.

Here's where you can get cheap petrol.