Costco Westgate has a reputation as the cheapest petrol in Auckland. But you pay a yearly fee to use it, it's a long drive for much of the city, and the other brands hand out discount dockets. This post checks the claim against our own daily Westgate prices, the Commerce Commission's national averages and Gaspy's live data from October 2026. It then works out how much fuel it takes to cover the membership, and when the drive isn't worth it.
Short answer: Usually, yes. On 15 October 2026 Costco Westgate sold 91 at $3.317 a litre, about 26c below Gaspy's national average of $3.575. Over the past four weeks it averaged about 19c below the Commerce Commission's daily national average for 91, and 23c below for diesel. It isn't always the cheapest pump in Auckland, though: a few discount sites in the central suburbs were 2–12c cheaper the same evening. At a 19c gap, the $60 Gold Star fee is covered after about 320 litres.
What is the Costco petrol price today?
New Zealand has one Costco, at 2 Gunton Drive, Westgate, in west Auckland. It sells three fuels: Unleaded 91, Premium 95 and diesel. Our Costco Westgate price page records the price every day. These are the figures for the 30 days to 15 October 2026 (we have no price for 18 September):
| Westgate | 15 Oct 2026 | 16 Sep 2026 | 30-day low | 30-day high | 30-day average |
|---|---|---|---|---|---|
| Unleaded 91 | $3.317 | $2.977 | $2.977 | $3.387 | $3.260 |
| Premium 95 | $3.507 | $3.167 | $3.167 | $3.547 | $3.441 |
| Diesel | $2.897 | $2.647 | $2.647 | $3.007 | $2.913 |
Prices rose sharply over the month. 91 went up 34c and diesel 25c, in line with the rest of the country as crude oil stayed high. Both 1News and Autotalk reported a record national average for 91 in early October, using Gaspy figures.
Is Costco petrol cheaper than the New Zealand average?
Yes, by a wide margin. The best day-by-day comparison is the Commerce Commission's fuel price monitoring. Since March 2026 it has published a regular report with a daily national average pump price for 91, 95 and diesel, drawn from Gaspy. The latest report, published on 15 October, has data up to 13 October.
| 13 October 2026 | 91 | 95 | Diesel |
|---|---|---|---|
| National average (Commerce Commission) | $3.613 | $3.795 | $3.241 |
| Costco Westgate (our data) | $3.367 | $3.517 | $2.947 |
| Costco cheaper by | 24.6c | 27.8c | 29.4c |
That was a wide day. Across the 27 days where we have both figures (16 September to 13 October), Costco was cheaper every day. The gap averaged 18.9c a litre for 91, 18.2c for 95 and 22.8c for diesel. The smallest gap was 10.9c for 91 (19 September) and 8.3c for 95 (19 September). The largest was 36.7c for diesel (9 October).
Gaspy's own public statistics told the same story on the evening of 15 October 2026. Its national averages were $3.575 for 91, $3.762 for 95 and $3.201 for diesel, based on 1,100 to 1,300 stations per grade. Costco was 25.8c, 25.5c and 30.4c below those. Costco's Premium 95 was cheaper than the national average for 91. (Whether your car needs 95 is covered in Costco 91 vs 95.)
MBIE also publishes weekly fuel price monitoring, but it's weekly and national, and its site blocked our attempts to download the latest figures. We used the Commerce Commission's daily series instead because it lines up with our daily prices.
Is there an Auckland average?
Not an official one. Neither MBIE nor the Commerce Commission publishes a regional average for Auckland, and we haven't found a published brand-by-brand average for Z, BP, Mobil, Gull, Waitomo, NPD, Challenge, Allied or Tank either. So we can't give you a fair "Costco vs Z" or "Costco vs Mobil" number.
One thing that used to make Auckland dearer is gone. The 10c-a-litre (11.5c with GST) Auckland regional fuel tax ended on 30 June 2024, so Westgate's price no longer carries an Auckland-only tax.
Is Costco the cheapest petrol in Auckland?
Often, but not always. Gaspy lists the five cheapest 91 prices in the country. At 9:08pm on 15 October 2026, all five were in Auckland, and all were below Costco's $3.317:
| Station (Gaspy, 15 Oct 2026) | 91 price | Compared with Costco |
|---|---|---|
| Tasman Epsom | $3.194 | 12.3c cheaper |
| U-GO Epsom | $3.196 | 12.1c cheaper |
| U-GO Quay St | $3.256 | 6.1c cheaper |
| Gull Kingsland | $3.296 | 2.1c cheaper |
| U-GO Panmure | $3.296 | 2.1c cheaper |
These are user-reported prices, and they move during the day. 15 October was a Thursday, the day Gull usually runs its Discount Days. Gull's site listed a promo every Thursday from 13 August to 8 October 2026. A post on ChoiceCheapies said Gull took 12c a litre off all grades from 6am on 15 October. We couldn't confirm that on Gull's own site. Discount Days are popular: in March 2026 1News reported several Auckland Gull sites ran dry after a 14c cut.
So Costco is reliably well below the average, but low-cost independents such as U-GO, Tasman and Gull (on a discount day) can beat it, especially in the central and eastern suburbs. NPD and Gull are now owned by the same group, but the Commerce Commission-cleared merger keeps the two brands separate.
Do discount dockets close the gap?
Not on their own. Most NZ fuel discounts are 6–10c a litre, while Costco's gap to the average has averaged about 18–23c over the past month. These were the main schemes in October 2026:
| Scheme | Where you use it | Discount |
|---|---|---|
| Foodstuffs Club+ (Pak'nSave, New World, Four Square) | Z and participating Caltex, or the store's own fuel site | 8c/L at Z and Caltex (max 100 L). At least 8c/L at North Island on-site stations (max $200 fill) |
| Z Rewards (Z app) | Z | At least 6c/L every day, up to 100 L |
| Woolworths Everyday Rewards | BP and GAS | BP advertises 6c/L every day on up to 50 L, sometimes more |
| Gull Discount Day | Gull | Varies by promo, for one day (14c in March 2026) |
| Waitomo app | Waitomo | A spin-to-win discount on fills of $20 or more. No fixed rate |
AA Smartfuel no longer exists. It ended on 31 January 2024 when Countdown (now Woolworths) moved to Everyday Rewards with BP. If a website still tells you to stack Smartfuel discounts, it's out of date.
Here's what that looks like on 13 October, with the national average standing in for a typical Z or BP:
- National average 91 minus an 8c Club+ docket: $3.533. Costco was still 16.6c cheaper.
- National average minus 6c (Z Rewards or Everyday Rewards): $3.553. Costco was 18.6c cheaper.
We haven't checked whether Club+ and Z Rewards discounts stack at the same fill, so we haven't added them together. Even stacked, 14c wouldn't close a 25c gap. A Gull Discount Day can get close, but usually only one day a week.
How much petrol pays for a Costco membership?
You need a membership to use the pumps, and your card is scanned before it will pump. Costco New Zealand's membership page listed two options on 15 October 2026:
| Membership | Annual fee | Who it's for |
|---|---|---|
| Gold Star | NZ$60 | Individuals |
| Business | NZ$55 | Businesses (registration required) |
Both include a free household card, and the card works at Costco warehouses worldwide. Our Costco NZ membership and payment guide covers Shop Cards, renewing before you fill up and which cards the pumps take. Divide the fee by the saving per litre to get the break-even:
| Saving per litre | Compared with | Litres to cover $60 | Litres to cover $55 |
|---|---|---|---|
| 24.6c | National average, 13 Oct | 244 | 224 |
| 18.9c | National average, 30-day mean gap | 317 | 291 |
| 10.9c | Narrowest gap in the past month | 550 | 505 |
| 5c | A cheap local station with a docket | 1,200 | 1,100 |
A worked example
Take a driver who covers 12,000 km a year in a car that uses 8 litres per 100 km. That's 960 litres a year.
- Against an average-priced station, the 30-day gap of 18.9c saves 960 × $0.189 = $181 a year. Take off the $60 Gold Star fee and they're $121 ahead.
- Against a Z or BP station with a 6c docket every fill, the saving is about 12.9c × 960 = $124. That's $64 ahead after the fee.
- Against a cheap independent that's only 5c dearer than Costco, the saving is $48. That doesn't cover the fee.
On a 50-litre fill, the 30-day gap is worth about $9.45.
Is the drive to Westgate worth it?
It depends where you start. A detour burns fuel and time, and the saving per fill is fixed by your tank size. This table assumes a 50-litre fill, a car using 8 L/100 km, 91 at Costco's 15 October price ($3.317) and the 18.9c average gap. Distances are rough extra kilometres for a special trip, not exact routes.
| Starting from | Extra driving (round trip) | Fuel burned on the detour | Saving on 50 L | Net per fill |
|---|---|---|---|---|
| Henderson or Hobsonville | About 10 km | 0.8 L ($2.65) | $9.45 | About $6.80 ahead |
| North Shore (Takapuna) | About 40 km | 3.2 L ($10.61) | $9.45 | About $1 behind |
| South Auckland (Manukau) | About 75 km | 6.0 L ($19.90) | $9.45 | About $10 behind |
| Hamilton | About 280 km | 22.4 L ($74.30) | $9.45 | Not worth a special trip |
Then there's the queue. Westgate is the only Costco fuel station in the country, and waits at busy times can wipe out a small saving if you value your time. The pumps open from 6am every day and close at 9:30pm on weekdays, 8:30pm on Saturday and 7:30pm on Sunday. See Costco Westgate fuel hours for public holidays.
The maths changes if you're going to Costco anyway. If you're already shopping at Westgate, or passing on State Highway 16 or 18, the detour costs nothing and every litre is pure saving.
Why is Costco petrol so cheap?
Costco treats fuel as a reason to visit the warehouse, not as a big earner. Its fiscal 2026 annual report, filed on 7 October 2026, says: "We believe our gasoline business enhances traffic in our warehouses; it generally has a lower gross margin percentage and lower SG&A expense". Fuel made up 11% of Costco's worldwide sales in the year to 30 August 2026.
In practice that means:
- Thin margins by design. Costco takes a smaller cut per litre because fuel customers come back and shop inside. Costco doesn't publish a New Zealand fuel margin, so we can't say whether it ever sells below cost.
- Membership fees carry the profit. Members pay up front each year, so Costco doesn't need to earn much on each litre.
- High volume. One large forecourt serves the whole Auckland region, so fixed costs are spread over many litres.
- Few extras. Three fuels, no café or convenience shop at the pump.
The wider market shows how much room there is. The Commerce Commission's 15 October report puts the average gap between the pump price and the refined cost of fuel at 43c a litre for 91 and 48c for diesel between 28 February and 13 October 2026. The Commission stresses this "should not be interpreted as 'profit'", because it also covers distribution, storage, running stations and discounting. But a 19c average gap to the national price suggests Costco takes a much thinner slice of that spread. For how this works in other countries, see why Costco fuel is cheap in Australia and Costco fuel prices in the UK.
How to check today's Costco Westgate price before you go
Prices move every few days, and in October 2026 they moved fast. Check today's Costco Westgate price before you set off, and compare it with the cheapest station on your normal route on the same day, not the national average. If a nearby independent is within a few cents, or Gull is running a discount day, the trip to Westgate may not pay.