The short answer
Yes — for most drivers, Costco gas is good. Its Kirkland Signature™ fuel is Top Tier certified, meaning it carries more engine-cleaning detergent than the EPA requires, and it usually sells for less than nearby stations. The base gasoline comes from the same major refineries that supply other brands in your area. The main trade-offs are the membership requirement, card-only payment, and sometimes long lines.
When people ask "is Costco gas good?" they usually mean one of two things: will it hurt my engine? and is it actually a better deal? Both have clear, evidence-based answers. Here is what the fuel-quality standards, an independent AAA study, and pump-price data actually show.
Is Costco gas Top Tier?
Yes. Costco's Kirkland Signature gasoline has been certified to meet the Top Tier Detergent Gasoline standard since 2014, in both regular and premium grades.
Top Tier isn't a marketing slogan — it's a performance standard created by a group of automakers(including BMW, General Motors, Honda, Toyota, Volkswagen, Audi, Mercedes-Benz, Stellantis, and Ford) who wanted gasoline with more cleaning detergent than the federal minimum. To carry the Top Tier license, a fuel must contain roughly three times the detergent additive the EPA requires, and it can't use the metallic additives that leave deposits behind.
Costco says its fuel goes further still: about five times the EPA's required detergent level in both regular and premium, blended into the gasoline on-site as tanker deliveries are made so Costco can control the dosage and quality itself.
Does Top Tier actually matter for your engine?
This is where it stops being marketing. In 2016, AAA commissioned an independent lab to run the question down: it cycled engines through the equivalent of 4,000 miles on six fuels — three Top Tier, three not — then took the engines apart and weighed the carbon deposits.
The result: non-Top Tier fuels left 19 times more carbon deposits on intake valves, injectors, and in the combustion chamber than Top Tier fuels. Those deposits are exactly what cause rough idling, hesitation, and a slow drop in fuel economy over time. AAA also found that switching to a Top Tier fuel can reverse some existing buildup over a few thousand miles.
The kicker: across a year of price tracking, AAA found Top Tier gas cost only about three cents a gallon more on average. "When it comes to selecting a gasoline, automakers got it right — Top Tier gasoline performs best," said AAA's Greg Brannon. With Costco you typically get the cleaner fuel without even paying that small premium.
Where does Costco gas come from?
A common worry is that cheap gas must be lower-grade or "leftover" fuel. It isn't. Costco doesn't own refineries — it buys finished gasoline from the same major refineries and distributors that supply other stations in each region, names like Chevron, Valero, Shell, or ExxonMobil depending on where you live.
In other words, the base gasoline in your Costco tank often came out of the same refinery as the fuel at the branded station down the street. What makes it "Kirkland Signature" is the Top Tier additive package Costco mixes in plus the company's guarantee: "All Kirkland Signature™ Fuel is guaranteed, just like the merchandise we sell inside the warehouse," Costco says.
What's actually in it — ethanol and octane
Costco gasoline is standard E10: it contains up to 10% ethanol, the same as most gas sold in the U.S., because federal renewable-fuel law requires ethanol in the supply. The ethanol content is labeled on every pump. If you're specifically hunting for ethanol-free gas, Costco generally isn't where you'll find it.
Octane is typical too — about 87 for regular and 91 for premium, though the exact numbers vary by state and altitude. The only real difference between Costco's regular and premium is the octane rating; both grades get the same Top Tier detergent dose.
Is Costco gas cheaper?
Usually, yes — and that's the other half of "good." Analysts who track pump prices put Costco's discount at roughly 5 to 25 cents a gallon below nearby stations, and warehouse clubs tend to hold their prices down longer when the market spikes. Reporting has pegged the typical gap at around 20 cents a gallon under the local average.
Costco can do this because gas is a loss-leader: it runs the pumps on thin margins to pull members into the parking lot, and its enormous purchasing volume lets it negotiate hard with suppliers. You can see how today's Costco prices stack up where you live on our live price pages — they're refreshed daily — or check our state-by-state price rankings.
The catch — membership, payment, and lines
Costco gas isn't friction-free:
- Membership. The pump reads your membership card, so you generally need a Costco membership — $65/year for Gold Star or $130 for Executive. The one workaround: anyone can fuel up with a Costco Shop Card, even without a membership (though you need a member to buy the card in the first place).
- Card-only payment. There's no cash at the pump in either country, and the accepted credit card flips at the border: in the U.S. it's Visa only (no Mastercard, American Express, or Discover), while in Canada it's the reverse — Mastercard only (no Visa or Amex). Debit and a Costco Shop Card work in both.
- The Costco Visa. If you pay with the Costco Anywhere Visa® Card by Citi, you earn 5% back on gas at Costco gas stations (on up to $7,000 a year in combined gas and EV-charging spend, then 1%) — savings that stack on top of the lower pump price.
- Lines and hours. Popular warehouses can have a wait, and fuel-center hours are shorter than a 24/7 station's.
So, is Costco gas good? The verdict
For most drivers, yes. You get Top Tier–certified fuel — the exact standard automakers ask for — typically at a below-market price, from the same refineries that supply other brands. The quality isn't a compromise, and the savings are real. Weigh that against the membership fee, card-only payment, and the occasional line, and for anyone who fills up regularly it's an easy call.
Frequently asked questions
Is Costco gas Top Tier?
Yes. Kirkland Signature gasoline has been certified to the Top Tier Detergent Gasoline standard since 2014, in both regular and premium grades. Top Tier is an automaker-backed standard that requires more engine-cleaning detergent than the EPA minimum.
Is Costco gas the same as Chevron, Shell, or other major brands?
Often the base fuel is. Costco does not own refineries — it buys finished gasoline from the same major refineries and distributors that supply other stations in each region, then blends in its own Top Tier detergent package on-site.
Is Costco gas bad for your car?
No. It meets the Top Tier standard that automakers recommend. An independent 2016 AAA study found Top Tier fuels left 19 times fewer carbon deposits in engines than ordinary gasoline.
Does Costco gas have ethanol?
Yes. Costco gasoline is E10 — up to 10% ethanol — like most fuel sold in the United States, because federal renewable-fuel law requires ethanol in the supply. The ethanol content is labeled on every pump.
Do you need a Costco membership to buy gas?
Generally yes, because the pump verifies an active membership card. The main exception is paying with a Costco Shop Card, which non-members can use once a member buys it for them.
Is Costco gas cheaper than other gas stations?
Usually. Analysts who track pump prices put Costco’s discount at roughly 5 to 25 cents a gallon below nearby stations, and warehouse clubs tend to hold prices down longer when the market spikes.
Sources & references
- Costco Wholesale — “Our Fuel Promise.” www.costco.com/fuel-promise.html
- Costco Wholesale — “Gasoline Questions & Answers.” www.costco.com/gasoline-q-and-a.html
- TOP TIER™ — Performance standard and licensed brands. www.toptiergas.com/
- AAA Newsroom — “Not All Gasoline Is Created Equal” (July 2016 engine-deposit study). newsroom.aaa.com/2016/07/aaa-not-gasoline-created-equal/
- U.S. News & World Report — “Costco Gas Prices vs. Local Stations: How Much Can You Save?” (2026). money.usnews.com/money/personal-finance/articles/costco-gas-prices-vs-local-stations-how-much-can-you-save-in-2026
- Citi — Costco Anywhere Visa® Card gas and EV-charging benefits. www.citi.com/credit-cards/understanding-credit-cards/costco-citi-card-gas-benefits
- U.S. Energy Information Administration — “How much ethanol is in gasoline, and how does it affect fuel economy?” www.eia.gov/tools/faqs/faq.php?id=27&t=10
Prices, rewards rates, and store policies change — figures were last reviewed in May 2026. Always confirm the price at the pump. This site is independent and not affiliated with Costco Wholesale Corporation.
