Who makes Kirkland Signature Gasoline (Regular 87 / Premium 91, sold at Costco fuel stations)?

Costco itself describes a regional multi-refiner model and names no single maker: "Q: Where does Costco get its fuel? A: Costco buys fuel from major refineries and distributors in each area. All Kirkland Signature Fuel is guaranteed, just like the merchandise we sell inside the warehouse" (archived: https://web.archive.org/web/20250227144738/https://www.costco.com/gasoline-q-and-a.html). The base gasoline at any Costco station comes from whichever major refiner or terminal serves that region, so there is no one manufacturer to name.

Kirkland Signature / Costco is a TOP TIER-licensed brand — the toptiergas.com brand list includes "Costco Wholesale USA / Costco Wholesale Canada / Costco Wholesale Puerto Rico" (archived: https://web.archive.org/web/20260702115937/https://www.toptiergas.com/gasoline-brands/). But TOP TIER is a detergent-performance standard set by automakers (GM, BMW, Toyota, Ford, VW, Honda, Stellantis and others), certifying the additive package, not the refinery of origin. Costco Auto Program's "Gasolines Are Not Created Equal" documents the additive dosing Costco adds at its own stations — "the optimum amount of detergent additive was approximately five times the government minimum" — and again names no refiner (archived: https://web.archive.org/web/20250119101547/https://www.costcoauto.com/automotive_articles/safety_and_technology/top_tier_gas_nozip.aspx).

Coverage consistently reports the same multi-source model and identifies no single refiner nationally: Costco buys commodity "brand-name" base gasoline from major refiners that vary by region and differentiates it by blending its own detergent additive at the pump. None of the outlets ties a specific refiner to Kirkland fuel — the most any source states is Costco's own line, "major refineries and distributors in each area."

Unlike motor oil — which has the API EOLCS licensee directory naming Highline Warren on the Kirkland oil licenses — retail gasoline has no deterministic maker registry. Finished gasoline is a fungible commodity: the base fuel at each Costco station comes from the nearest refinery / pipeline terminal (branded or unbranded rack), which varies by market. No code-on-the-product route resolves a maker.

No recall names a Kirkland or Costco gasoline refiner. CPSC SaferProducts returned no Kirkland/Costco gasoline recall (retail gasoline sits under EPA fuel programs and state weights-and-measures oversight rather than CPSC). No enforcement action surfaced a co-supplier.

Enthusiast forums speculate that specific majors (Exxon, Chevron, Valero, Shell, Marathon) supply given regions and debate whether Costco's detergent additive is Techron-like, but the only consistent point is that the supplier varies by location and is not disclosed. Tier-6 chatter, nothing citable to a specific maker.

Not applicable — retail gasoline is delivered by domestic refinery and pipeline/terminal, not imported under bills of lading, so the customs route yields nothing for this product.