Costco fuel is often some of the cheapest in town, and cheap fuel makes people wonder what is going into the tank. This post sets out what Australian law says every litre must meet, what Costco says about its Kirkland Signature fuel, what is known about who supplies it, and how it compares with Shell V-Power, BP Ultimate and Ampol Amplify.
Short answer: Yes, Costco fuel is good. Every litre of petrol and diesel sold in Australia must meet the national fuel quality standards made under the Fuel Quality Standards Act 2000, whether it comes from Costco, a supermarket servo or Shell. Costco says all its fuels contain deposit control additives. It does not currently publish who supplies the base fuel; a 2019 press report said it was Mobil.
What standard does Australian fuel have to meet?
Fuel quality in Australia is set by federal law, not by brand. The Fuel Quality Standards Act 2000 makes it an offence, and a civil penalty, to supply fuel that does not comply with the fuel standards (sections 12 and 12AA). The standards themselves sit in determinations made under the Act:
| Fuel | Current determination | Some key limits |
|---|---|---|
| Petrol (91, 95, 98, E10) | Fuel Quality Standards (Petrol) Determination 2024 | RON 91.0 minimum for the 91 grade, 95.0 for the 95 grade; ethanol 10% maximum; benzene 1% maximum |
| Diesel | Fuel Quality Standards (Conventional Diesel) Determination 2025 | Sulfur 10 mg/kg maximum; biodiesel 5% maximum; derived cetane number 51 minimum where it contains biodiesel |
| E10 labelling | Fuel Quality Standards (Ethanol) Information Standard 2019 | Pumps selling ethanol blends must say the fuel may contain up to 10% ethanol |
The standards cover octane, sulfur, aromatics, benzene, lead, gum, oxidation stability, distillation, water and sediment, ethanol and biodiesel content, and more. A servo cannot sell "budget" fuel that falls short of them. Note that the petrol standard has only two legal grades, 91 and 95. "98" is a label the seller puts on fuel that must still clear the 95 grade's floor; the extra octane is the seller's claim.
What changed in 2026?
Because of the Middle East supply crisis, the government temporarily eased two limits in March 2026. As the NRMA reported, petrol was allowed up to 50 ppm sulfur, up from the 10 ppm limit introduced in late 2025, and the diesel flash point minimum dropped from 61.5°C to 60.5°C. The current petrol determination now steps sulfur down to 40 mg/kg from 1 October to 31 December 2026, and back to 10 mg/kg from 1 January 2027. The diesel flash point returned to 61.5°C on 1 October 2026.
These changes applied to every seller, not just Costco. The NRMA's Peter Khoury said the higher-sulfur petrol is "not really dirty fuel in the sense that it's going to hurt your engine", and "the same fuel we were buying 12 months ago and beyond."
Is there a Top Tier fuel standard in Australia?
No. Top Tier is a voluntary detergent standard written by carmakers and used mainly in the Americas. Its licensed brands list covers markets including the USA, Canada, Mexico and Japan, but not Australia. Costco is licensed as Top Tier in the USA, Canada, Mexico, Puerto Rico and Japan only.
A lot of "is Costco fuel good" answers online come from the US and lean on Costco's Top Tier badge there (our US Top Tier post covers it). None of that applies at an Australian bowser. Here there is no independent badge that ranks one brand's additives above another's. Each brand makes its own claims.
What fuel does Costco sell in Australia?
Costco sells fuel at 14 of its 15 Australian warehouses (Ringwood in Victoria has no fuel station). Every site sells Premium 98 and diesel. The third fuel depends on the state:
| Grade | Where Costco sells it |
|---|---|
| E10 | NSW and Queensland sites: Lidcombe (Auburn), Casula, Marsden Park, Boolaroo (Lake Macquarie), North Lakes, Bundamba (Ipswich), Coomera (Gold Coast) |
| Unleaded 91 | Canberra, Moorabbin, Epping, Ardeer, Adelaide, Perth Airport, Casuarina |
| Premium 98 | All 14 |
| Diesel | All 14 |
The split lines up with state ethanol mandates. NSW has required larger fuel retailers to sell a share of ethanol since 2007 (ACAPMag), and Queensland has a similar mandate. Costco has not said that is why, so treat it as our reading, not Costco's. If your car can't take E10 and you fill up at a NSW or Queensland Costco, use Premium 98. Our Costco fuel grades guide covers the mandates, RON numbers and the price gap between grades.
The full list is on our Costco fuel stations page, with times on Costco fuel opening hours.
Who supplies Costco fuel in Australia?
Costco doesn't currently say. Here is what we found, and how much weight each piece deserves:
- Costco's own fuel page (costco.com.au/fuel-station) talks about additives, tank monitoring and vapour recovery, but names no refiner or wholesaler.
- Costco's fuel FAQ (PDF, dated 16 December 2014) covers payment and says "Costco Fuel is just another quality product". It does not name a supplier. It does say a "MSDS or fuel specification sheet" is "readily available from Costco upon request".
- A 2019 press report said Costco used Mobil. In an article republished by ACAPMag from the Queensland Times, written around the Ipswich opening: "Currently Costco sources its quality fuel from Mobil which is specified to meet Australian Standards." That was true, as reported, in 2019. We could not confirm it is still true across all 14 sites in 2026.
- Many websites repeat the Mobil line word for word, often without a date. They trace back to the same 2019 wording, so they don't add evidence.
What we can say with confidence is how supply works here. Australia now imports most of its fuel, and a few large wholesalers (Ampol, Viva Energy, BP and ExxonMobil/Mobil) bring it in and run the terminals. Retailers without refineries, Costco included, buy from them. The finished fuel must meet the national standard whoever buys it. The brand difference is mostly the additive. Our US post on where Costco gets its gas explains the same idea for America, but its supplier facts are US-only.
If you want the facts for your own site, ask the warehouse for the fuel specification sheet. Costco says it will provide one.
What additives are in Costco fuel?
Costco Australia's fuel page says:
- "Deposit control additives are the main points of difference between fuel brands."
- "Our Kirkland Signature Fuels include additives designed to minimise engine deposits that are harmful to a vehicle's performance and emissions."
- "All Costco fuels contain deposit control additives that have been tested and are proven to have positive effects on your vehicle's engine performance."
What Costco Australia does not publish:
- The name or maker of the additive.
- A dose, such as the "five times" the US minimum figure Costco uses in America.
- Any independent test of its Australian fuel against other brands.
So the additive claims are Costco's own. They are the same kind of claims every brand makes, and none has been tested head to head against other Australian brands in public.
Is Costco diesel good?
It is diesel that must meet the Conventional Diesel Determination: 10 mg/kg sulfur maximum, up to 5% biodiesel, the cetane minimum in the table above and the flash point minimum noted earlier. Costco says all its fuels, diesel included, carry its deposit control additive.
Costco's Australian site does not market a separate "premium diesel" or publish a cetane figure. That differs from the UK, where Costco sells Kirkland Signature Premium Diesel. Costco's FAQ notes the Australian sites have "4 pumps that dispense high flow diesel specially installed for trucks" (the number is from the 2014 FAQ and may differ by site).
On 15 October 2026, Costco diesel across our 14 Australian sites averaged 270.4c/L. Live prices are on our Costco diesel page.
How does Costco fuel compare with Shell V-Power, BP Ultimate and Ampol Amplify?
The big brands sell premium fuels with their own additive packs, and say so:
- Shell V-Power is a 98 octane fuel sold in Australia by Viva Energy, which describes it as designed to give "performance and efficiency benefits". Viva says it has friction modification and cleaning technology.
- BP Ultimate is a minimum 98 octane petrol that BP says "cleans away harmful dirt" in engines and helps stop it coming back.
- Ampol Amplify Premium 98 is, per Ampol, its "highest octane petrol". Amplify Premium Diesel "contains advanced additives to help restore and maintain fuel injector cleanliness".
Here is how they line up on what is published:
| Costco Premium 98 | Shell V-Power | BP Ultimate 98 | Ampol Amplify 98 | |
|---|---|---|---|---|
| Meets national petrol standard | Yes | Yes | Yes | Yes |
| Advertised octane (RON) | 98 | 98 | 98 minimum | 98 |
| Cleaning additive | Yes (Costco's claim) | Yes (Viva's claim) | Yes (BP's claim) | Yes (Ampol's claim) |
| Friction modifier claimed | Not stated | Yes | Not stated on page | Not stated on page |
| Public independent head-to-head test | None found | None found | None found | None found |
Nobody has published an Australian test that ranks Costco's additive against Shell's, BP's or Ampol's. Anyone who says Costco fuel is clearly worse, or clearly as good as V-Power, is going beyond the evidence.
Do you need 98 at all?
Only if your car needs it. The NRMA's Peter Khoury put it simply: "if you don't need it, don't use it", because "you just end up paying a lot of money … for no real reason" (4BC). Check the fuel filler flap or the owner's manual. If it says 95 or above, use Premium 98 at Costco, since Costco does not sell 95.
At Costco, 98 costs more. In our 15 October 2026 reading, Costco Premium 98 was an average of 22.8c/L above E10 or Unleaded 91 at the same site, with a range of 16c to 28c. See our Australia fuel hub for today's numbers.
Will Costco fuel damage your engine?
No. The common worries do not hold up:
- "Cheap fuel is lower quality." Costco's low price comes from its members-only, high-volume model and thin margins, not a lower spec (why Costco fuel is so cheap). The fuel must meet the same national standard as everyone else's.
- "It's watered down." The standards limit water and sediment. We found no evidence of Costco selling watered-down fuel.
- "It will void my warranty." Carmakers specify an octane and whether a car can use E10. They don't specify a brand.
- "Discount fuel has no additives." Costco says all its fuels contain deposit control additives.
- "Costco 98 isn't really 98." We found no public test showing that. The law sets 95 as the minimum for premium grades; selling fuel as 98 is the seller's representation. If you doubt it, the spec sheet is available on request.
Contaminated deliveries can happen at any servo, branded or not. If your car runs badly straight after filling up anywhere, keep the receipt and contact the site. Star ratings for a site such as Lidcombe or North Lakes reflect queues and wait times as much as anything; a review is not a fuel test. For the US take on these myths, see is Costco gas bad for your car.
Should you fill up at Costco?
For most cars, yes. If your car takes 91 or E10, Costco's base grade meets the same national standard as any other servo, carries a deposit control additive by Costco's account, and usually costs less. Buy Premium 98 if your car needs 95 or higher, or can't use E10 at a NSW or Queensland Costco.
You need a Costco membership to use the pumps (who can buy Costco fuel). Find your nearest site with Costco fuel near me, or browse by state: NSW, Victoria, Queensland, South Australia, WA and the ACT. All Australian prices are on the Costco Australia fuel hub.