Kiwis across the country are packing up the car and searching for the best place to spend their petrol dollar as they travel to or from holiday destinations.

They should be thankful they don't have to do it on Waiheke Island.

On Saturday the BP station at Oneroa, Waiheke had what could be the country's highest petrol price, with Regular 91 fuel selling for $2.11 per litre, 26 cents more a litre than the national average fuel price of $1.85, according to online database pricewatch.co.nz.

Auckland was also home to the country's cheapest petrol, with numerous stations in southern suburbs like Mt Wellington, East Tamaki and Papakura selling petrol for $1.67 a litre.

Generally northern regions like Waikato, Auckland, Bay of Plenty had cheaper petrol than the mainland and southern North Island. The highest price identified on the mainland islands was $2.03 at a Gasoline Alley (GAS) station in Northland.

AA petrol price spokesperson Mark Stockdale says price discrepancies across the country were caused by something his organisation called the "Gull effect".

Because Gull stations had low operating costs, they were able to offer cheaper fuel than their competitors. This forced other fuel chains near Gull stations to drop their prices to match.

Newlywed couple Sam Duff and Jimmy Jansen, of Wellington, have spent less of their South Island honeymoon budget on petrol with the price dropping 15c a litre since September.

Meaning cheaper petrol for regions where Gull operated - Auckland, Waikato, Bay of Plenty Manawatu, Manawatu and Hawkes Bay. But the rest of the country was having to pick up the slack.

Gull-less areas like Wellington, Taranaki, and the entire South Island, had had their petrol prices hiked by other companies to compensate for the money they were losing matching Gull's low prices, Stockdale explained.

The "Gull effect" has been felt by a Hamilton family gearing up for a 750km return trip

The low prices are more important for some Kiwis than others.

Dion Tupara, 39, is originally from Gisborne so travels there regularly for holidays with his wife and twin sons. The trip can cost anything between $140 to $170 depending on fuel prices.

"Because of that I've worked out where the cheapest places to fuel up on the journey are," he says.

And for Dion, the cheapest petrol was at a Gull station.

"I tend to select where to fuel up in Hamilton based on where the cheapest fuel is - that's generally the Gull on Norton Rd.

"If I need fuel for the return journey I usually stop in Whakatane as there is a lot of competition there, so it makes it a lot cheaper than fuelling up in Gisborne."

The Z in Whakatane was generally his choice because it was beside a Gull, so always had competitive prices.

But even Southerners paying more than their North Island relatives for petrol have something to smile about at the pump this summer. Nationwide, the price of petrol has dropped by around 15 cents per litre in the last 3 months.

Newlywed South Island couple Sam Duff and Jimmy Jansen say it was nice to know less of their honeymoon budget would be going toward gas.

"We saved up some money for our holiday, which included budgeting for petrol," Sam says.

"It's nice to have a bit of extra cash that we can spend on treats while we're on our honeymoon."

His husband says while he "quite liked Z stations" for their pre-pay convenience, paying more for petrol in remote places was sometimes necessary.

"If it was a choice between running out of petrol on the side of the road, and paying a bit more, I know which one I would choose," Jimmy says.

As for Waiheke, resident Marcus McKenzie was not too perturbed by the high price he pays at the pump. Marcus says it was a fact of life when you live on an island and fuel had to have to come over from Auckland on a dedicated barge, not a regular ferry service.

The AA recommended motorists keep an eye on petrol prices on their holiday journeys. If a station offered fuel at a price lower than the national average of $1.85 per litre, it might be worth pulling over to fuel up.

- Stuff