The short answer
Costco doesn't own refineries and doesn't make its own gas. It buys finished — usually unbranded — gasoline from the same major refineries and distributors that supply other stations in each region, often through the same shared pipelines and terminals. What makes it Kirkland Signature™ is the Top Tier detergent package Costco blends in on-site (about five times the EPA minimum) plus its money-back guarantee. So the base fuel is essentially the same as the branded station down the street; the real differences are the added detergent and the lower price.
"If Costco gas is so cheap, where does it actually come from?" is one of the most common questions members ask — usually with a worry hiding inside it that bargain fuel must be lower-grade or "leftover." It isn't. Here's how gasoline really travels from a refinery to your tank, where Costco fits in, and what actually makes its fuel different.
Costco doesn't refine its own gas
Start with what Costco isn't: an oil company. It owns no refineries and doesn't blend the base gasoline itself. In its own words, Costco "receive[s] our gasoline from the same major refineries and distributors that supply all of the gas stations in an area" — and crucially, it "does not purchase gasoline from a single supplier." The fuel it buys is typically unbranded, sourced regionally and varying by warehouse — and even by delivery.
How gasoline actually gets to the pump
To see why "the same refineries" is more than a marketing line, it helps to follow the supply chain the U.S. Energy Information Administration lays out. Gasoline is largely a fungible commodity: once it meets a spec like 87 octane, one batch is interchangeable with another.
- 1
Refinery
Crude oil is refined into gasoline. Refineries make nearly all U.S. fuel.
- 2
Pipeline
Fuel ships in batches through shared pipelines, where products from different refiners commingle.
- 3
Bulk terminal
Gasoline is stored and tested to spec. Competing brands draw from the same terminals.
- 4
Blending rack
Ethanol and each company’s detergent additive are injected — the gas becomes “finished.”
- 5
The pump
Tanker trucks deliver finished fuel to stations — including your Costco.
Two steps in that chain do the heavy lifting. In the pipelines and bulk terminals, "some mixing, or commingling, of products occurs" — fuel from different refiners is pooled in shared tanks. And competing companies "may purchase their gasoline at the same bulk storage and distribution terminal." That's why the gas in your Costco tank may have come from the exact same refinery as the name-brand station next door.
"Unbranded" doesn't mean lower quality
The word unbrandedtrips people up. It doesn't describe a worse grade of fuel — it describes fuel that hasn't had a major oil company's proprietary additive injected at the terminal. The EIA is blunt about how small that difference is: the only real distinction between brands is "the small amount of additives they might blend into gasoline before delivery to their fueling stations." Many stations are simply "unbranded dealers that sell gasoline produced by different companies."
Every gallon, branded or not, must also clear the EPA's minimum detergent requirement. So Costco starts from the same base fuel as everyone else — and then adds more to it.
What makes it "Kirkland Signature"
Here's where Costco diverges from a generic discount pump. Rather than rely on a terminal's additive, Costco blends its own Top Tier detergent package into the fuel on-site as tanker deliveries are made, dosing it at about five times the EPA's required detergent level in both regular and premium. Kirkland Signature gasoline has been Top Tier certified since 2014 — the automaker-backed standard that requires far more cleaning detergent than the federal minimum and bans the metallic additives that leave deposits.
That additive is the part that actually matters for your engine. An independent AAA study found that non-Top Tier fuels left 19 times more carbon deposits on intake valves and injectors than Top Tier ones. Costco also backs the finished product the way it backs everything else, promising that "all Kirkland Signature™ Fuel is guaranteed." We dig into the engine-health side of this in Is Costco gas good?, and the grade-by-grade breakdown lives in Costco gas types explained.
So is it the "same gas" as the big brands?
Largely, yes — and that's the reassuring part. The base gasoline frequently comes from the same refineries and terminals that feed Chevron, Shell, ExxonMobil, Valero, or whoever else operates near you; the brand on the canopy mostly signals which detergent got mixed in. Costco's version is unbranded base fuel plus a Top Tier additive dosed higher than most. The cheap price isn't a tell that the fuel is inferior — it's a tell about Costco's business model.
Why so cheap, then? Volume.
Costco is one of the largest fuel retailers in the country. Its fiscal-2024 annual report shows it operated 719 gas stations and that gasoline made up roughly 12% of its $249.6 billion in net sales. Buying at that scale lets Costco negotiate hard on wholesale fuel, and because gas is a deliberate loss-leader — run on razor-thin margins to pull members into the parking lot — it passes the savings through at the pump. You can see how today's Costco prices compare where you live on our live price pages.
Frequently asked questions
Does Costco make its own gas?
No. Costco does not own or operate refineries and does not refine or blend the base fuel itself. It buys finished gasoline from the same major refineries and distributors that supply other stations in each region, then adds its own Top Tier detergent package.
Is Costco gas the same as Chevron, Shell, or Exxon?
Often the base gasoline is. In any given area, fuel from different brands moves through shared pipelines and terminals and is commingled, so the gas in a Costco tank may have come from the same refinery as the branded station down the street. The differences are the detergent additive each brand blends in and the price.
Is Costco gas just cheap “unbranded” fuel?
The base fuel Costco buys is typically unbranded, but that is not the same as bare-minimum. Costco blends in its own Top Tier detergent — about five times the EPA-required level — so the finished Kirkland Signature fuel carries more cleaning additive than ordinary gas, not less.
Where does my local Costco’s gasoline come from?
Whatever refineries and distribution terminals serve your region — it varies by location and even by delivery, and Costco does not publish a per-station source. By design it is the same regional supply that feeds the other stations near you.
Why is Costco gas cheaper if it’s the same fuel?
Lower price doesn’t mean lower-grade fuel. Costco buys enormous volumes (it ran 719 gas stations in fiscal 2024) and treats fuel as a loss-leader to pull members into the warehouse, so it runs the pumps on thin margins. The savings come from the business model, not from cheaper gas.
Does Costco add ethanol to its gas?
Costco sells standard E10 (up to 10% ethanol), like most U.S. gasoline. Ethanol is blended into finished gasoline at the distribution terminal, not at the warehouse, and the content is labeled on every pump.
Fuel supply arrangements, store counts, and policies change over time — figures were last reviewed in June 2026. This site is independent and not affiliated with Costco Wholesale Corporation.
