The cheapest and most expensive places to fuel up in Auckland

Petrol prices across Auckland are varying drastically, with a 61 cent per litre difference between the cheapest and the priciest.

With the fuel tax subsidy finishing at the end of June, the cost of filling up is set to rise for everyone. But why is there such a major disparity in Tāmaki Makaurau?

RNZ visited Costco in West Auckland, where fuel costs are among the cheapest in the region. One motorist, Jake, was filling up not just his car but also three 10-litre tanks, for his other vehicles. He said he visits the 27-pump petrol station twice a week.

On 14 June, unleaded 91 was $2.11 per litre and diesel was $1.62. Only those with a $60 Costco annual membership can access the pumps.

Silverdale farmer Steve was also there to fill his truck and several 20 litre containers.

"I fill up for farm fuel as well as diesel for my truck. It's the cheapest in town, so why wouldn't you?"

Another driver, Brent, often made a 100km round trip from his home in Milldale to his workplace in Avondale, going via Costco in Westgate for fuel. He told RNZ the drive was worth it for the "massive difference" in petrol prices.

Less than five minutes' drive away in Henderson, a Mobil station charges 44 cents more than Costco, with unleaded 91 fetching $2.55/L and $2.02 for diesel.

One driver, Ben, said he tried to buy petrol in South Auckland where prices are more affordable. He said fuel costs make it hard to cope.

"We're all broke," he told RNZ.

A glimpse at petrol prices around Auckland:

• Z, Te Atatu Peninsula - unleaded 91: $2.52, diesel: $2.02
• BP, Herne Bay - unleaded 91: $2.55, diesel: $2.04
• BP, Northcote - unleaded 91: $2.44, diesel: $1.96
• Pak'nSave, Wairau -unleaded 91: $2.39, diesel: $1.97 (with a supermarket receipt)
• Z, Panmure - unleaded 91: $2.52, diesel: $2.02
• Caltex, Newton - unleaded 91: $2.38

The priciest petrol was found at a Mobil station in St Heliers. At $2.72 for unleaded 91, it was 61 cents more per litre of unleaded fuel than Costco.

At the Mobil in St Heliers, driver Alice told RNZ she got petrol wherever it was most convenient, but said she does watch out for where she can get a saving.

"When I've got time, that is when… Pak'nSave sometimes is quite a good deal. So it all comes down to what's happening, and how much of a rush I'm in."

But why?

So why the discrepancy across the city? AA's fuel spokesperson Terry Collins said the 61c difference comes down to competition.

"That compares to something like about 33c, 35c for Christchurch and for Wellington.

"So it appears that the major cities that have more service stations, more competition will have a larger price differential.

"Smaller places, Tauranga, Nelson, Matamata, have a smaller differential because there's basically less competitors in the market."

Collins said the AA had seen price differences of up to 65 cents for diesel across Auckland.

He added that a number of factors are at play.

"You have to buy futures for fuel, you buy it into the future. So some companies might have got a better deal because of their volume, where they could have got it at a lower landed cost.

"Others may just charge because the market will bear it, due to their positioning or other things.

"Generally those price differences are around competition for volume. This is a volume model, where they try to sell as much fuel as they can, and if it means that they have to just reduce the margins a little bit to sell more volume, sometimes it's more profitable to do that.

"Other times they're prepared to sell less volume at a higher profit because that's the best way of maximising their return."

At a Z station in Panmure, Martin was filling up his car.

"It's very expensive if you use your private vehicle, but at least this is a work vehicle. But it does impact on the business as well."

He told RNZ he would sometimes drive to get a better price, but he had to weigh up if it was really worthwhile to use more petrol to go a longer distance.

The self-service Caltex on Newton Road in central Auckland has become popular, with only a forecourt of pumps and no shop. On 14 June, unleaded 91 was $2.38.

Customer Maree was there with a lifehack to help save precious dollars.

"This seems to be the cheaper one around here, and Wednesdays is the 10c day. I split it into a couple of sets of $40 to get the extra stacking.

"I've got probably about a quarter of a tank left and I've put in $40 to get the 10 cents. Now I'm going to put in another $40 to get another 10 cents stacked up."