Costco Fuel Grades in Australia: Unleaded 91, E10, Premium 98 and Diesel

Costco fuel stations in Australia have only three fuels at the bowser, and which three depends on your state. This post covers which grade each Costco sells, why New South Wales and Queensland get E10 instead of Unleaded 91, whether any Costco sells 95, what the RON numbers mean, and how much more Premium 98 costs, using prices from our own tracker.

Short answer: Every Australian Costco fuel station sells Premium 98 and diesel. The base petrol is E10 at the seven NSW and Queensland sites and Unleaded 91 at the seven sites in Victoria, South Australia, Western Australia and the ACT. No Costco in Australia sells 95. On our 15 October 2026 reading, Premium 98 averaged 253.0c/L, 22.8c/L more than the base grade.

What fuel grades does Costco sell in Australia?

Each of the 14 Costco fuel stations sells one base unleaded, Premium 98 and diesel. The warehouse data on costco.com.au lists the grades for every site, and we checked it on 15 October 2026. Marsden Park and Bundamba (Ipswich) list "E10, Premium 98, Diesel". Moorabbin and Canberra list "Unleaded 91, Premium 98, Diesel". Every other site matches its state.

The Ringwood warehouse in Victoria has no fuel station. For addresses and maps, see every Costco fuel station in Australia, or the Australian Costco fuel prices hub for today's numbers.

No site sells both E10 and Unleaded 91. Our price feed shows one or the other at each station across the last 30 days, never both.

Does Costco have 95 petrol?

No. We found no Costco in Australia that sells 95. Costco.com.au lists only E10 or Unleaded 91, Premium 98 and diesel for each site, and our price feed has no 95 reading for any of the 14 stations.

The state price reporting schemes agree. On 15 October 2026, the Western Australian FuelWatch feed listed Costco Perth Airport and Costco Casuarina under Unleaded Petrol, 98 RON and Brand Diesel, and under neither Premium Unleaded (95) nor plain Diesel.

If your car needs 95, Costco's Premium 98 meets that requirement. A higher octane than your car asks for does no harm.

Across the Tasman it is different. Costco's Westgate station in Auckland sells 91 and 95, not 98 (see Costco 91 vs 95 in New Zealand), as Driven reported when it opened.

Why do NSW and Queensland Costcos sell E10 instead of 91?

Both states have ethanol mandates aimed at big service stations. Costco fuel stations are some of the busiest in the country, so they are caught by them. Victoria, South Australia, Western Australia and the ACT have no mandate, and Costco sells Unleaded 91 there.

New South Wales

The NSW Biofuels Act 2007 applies to "volume fuel retailers". Per the NSW EPA's biofuels guidelines, these are operators of a "volume fuel service station", which is a site where "3 or more types of petrol or diesel fuel are sold" and total petrol and diesel sales exceed 1,800,000 litres over six months, for two six-month periods in a row. Every Costco in NSW sells three fuels, and a Costco fuel station sells far more than that.

A volume fuel retailer must make sure:

• 6% of the total volume of petrol it sells is ethanol
• 2% of the total volume of diesel it sells is biodiesel
• E10 is "as accessible to customers as regular unleaded petrol or any other type of petrol" at each site

The NSW Government's E10 history page explains that the state dropped a plan to phase out regular unleaded in 2012. So the law does not ban Unleaded 91. Costco chose to sell E10 as its only regular grade, which is one simple way to meet both the 6% target and the accessibility rule with just three bowser grades. Costco has not published its reasons, so treat that as our reading of the rules.

Queensland

Queensland's mandate sits in the Liquid Fuel Supply Act 1984. Business Queensland says "4% of the total volume of regular unleaded petrol sales and ethanol-blended fuel sales by liable fuel retailers must be biobased petrol (ethanol)". The mandate covers retailers with 10 or more sites, or a single site selling above a quarterly petrol volume threshold, which a Costco would pass easily. As in NSW, the law sets a share, not a ban on 91, and Costco has chosen E10 as its only regular grade.

Neither state requires the ethanol to be in premium, and costco.com.au lists Premium 98 separately from E10. Costco does not publish whether its 98 contains any ethanol, so check the bowser label.

What does the number on the bowser mean?

The number is the Research Octane Number (RON). It measures how well petrol resists knock, which is fuel igniting before the spark. Higher-compression and turbocharged engines need higher octane.

The national Fuel Quality Standards (Petrol) Determination 2024 sets two grades: a 91 RON grade with a 91.0 minimum and a 95 RON grade with a 95.0 minimum. It caps ethanol at 10%. There is no separate legal grade for 98. A "98" is sold under the 95 grade's rules and marketed at 98.

Australia uses RON. The US and Canada post the Anti-Knock Index, an average of RON and a harsher test, so their numbers are lower for the same fuel. That is why a US Costco sells "87" and "91" while an Australian one sells 91 and 98. Our US Costco gas grades guide covers the American numbers. Don't compare them directly.

The E10 figure comes from the NSW Government's E10 facts page, which says E10 blends RON 91 petrol with 9–10% ethanol and "Blending the ethanol at this ratio increases the RON to 94."

Which Costco fuel does your car need?

Use what your car's maker says. It is printed inside the fuel flap and in the owner's manual.

• Your car says 91 or regular unleaded. Buy E10 or Unleaded 91, whichever your Costco sells, as long as the car is E10 compatible (see below). Premium 98 gives you no benefit you'll notice in an engine built for 91.
• Your car says 95 minimum. Buy Premium 98. Costco has no 95, and E10 at around 94 RON is below what the car needs. The NSW Government says that if the maker recommends premium, "Neither E10 (RON 94) or regular unleaded petrol should be used in those vehicles."
• Your car says 98. Buy Premium 98.
• Your car is diesel. Buy diesel. Never put petrol in a diesel engine.

If your car needs Unleaded 91 and the nearest Costco is in NSW or Queensland, note those sites sell E10 instead. Their only other petrol is Premium 98, which any car that takes 91 can use.

Can my car use E10?

Most can. The NSW Government says "The majority of modern cars running on unleaded petrol today are compatible with E10", and that most petrol cars sold here since 1986 were designed for RON 91. It also says high-performance cars and older cars, especially those built before 1986 or with carburettors, shouldn't use it.

To check a specific car, use the NSW Government E10 compatibility check. It draws on manufacturer information and covers petrol cars built after 2000. If your car isn't listed, ask the manufacturer. Motorbikes, boats and small engines need a check of their own.

E10 also carries less energy. The NSW Government says E10 has "around 3% less energy" than RON 91, which can mean around 3% more fuel used. At the E10 prices on our snapshot, 3% is roughly 7c/L. No Costco sells E10 and 91 side by side, so we can't show that trade-off at one site.

What is the Costco 98 fuel price?

On our 15 October 2026 reading, Premium 98 cost 22.8c/L more than the base grade on average across all 14 Costcos. That is about $13.70 extra on a 60-litre fill.

The gap is wider at the E10 sites. There Premium 98 averaged 25.0c/L above E10 (range 22c to 28c). At the Unleaded 91 sites it averaged 20.5c/L above 91 (range 16c to 23c). Over the 30 days to 15 October, the gap averaged 22.8c at E10 sites and 21.0c at 91 sites, so the snapshot is typical.

All prices are in cents per litre from our 15 October 2026 snapshot. Costco changes prices often, so check the station page or find the Costco fuel station nearest you before you drive.

Two things stand out. Premium 98 at Costco is cheaper than diesel at every site (for how Costco compares with other servos, see why Costco fuel is so cheap). And the WA stations had the cheapest diesel of the 14 Costco sites, and shared the cheapest 98 with Adelaide, on this reading, though the WA price cycle can flip that within days.

Does Costco sell premium diesel?

Costco sells one diesel at every Australian fuel station. Costco.com.au simply calls it "Diesel". The state price schemes file it as a premium or branded diesel. WA FuelWatch lists both Perth Costcos under "Brand Diesel", not plain "Diesel", and other price sites show it as Premium Diesel. You can't choose between a standard and a premium diesel at Costco.

Costco Australia does not publish a specification or additive details for its diesel that we could find. All diesel sold here must meet the national Fuel Quality Standards (Conventional Diesel) Determination 2025, which caps sulfur at 10 mg/kg and allows up to 5% biodiesel. According to the NRMA, premium diesels are generally formulated to "reduce foaming at the pump, run cleaner in your system and reduce the amount of black soot", and it calls claims of better mileage "anecdotal at best".

Diesel was the dearest fuel at every Costco on our snapshot, averaging 270.4c/L. For today's prices by station, see Costco diesel prices in Australia. If you want to know about Costco diesel in other countries, see does Costco sell diesel.

Can you buy Costco fuel without a membership, and when is it open?

No. Costco fuel in Australia is for members only (who can buy Costco fuel), and you pay at the bowser with a PIN card (how to fill up and pay). Most sites open from 6am on weekdays. Hours differ by site, so check Costco fuel opening hours before you go. State pages list every station's grades and today's prices: NSW, Victoria, Queensland, South Australia, Western Australia and the ACT.

What we could not confirm

• Costco's reasons. Costco has not said why it sells E10 instead of 91 in NSW and Queensland. The mandates are the likely reason, but that is our reading.
• Whether Premium 98 contains ethanol. Neither mandate requires ethanol in premium, and costco.com.au doesn't list it as an ethanol blend. Costco publishes no specification, so check the label on the bowser.
• Who supplies Costco's fuel, and what additives it contains. Costco Australia does not say on its website, and we found no current Costco statement on either. Our Costco fuel quality post sets out what is known, including a 2019 report naming Mobil.