What Brand Is Costco's Gas And How High-Quality Is It?

Stopping at your favorite retailer's on-site fuel center after a long shopping trip can be a convenient way to fill up. This is also true of Costco's fuel centers where traffic only goes one way, but once you're done, you can pull out and head home. Costco as a company carries and sells Kirkland Signature, a brand that goes beyond the minimum detergent requirements set by the EPA.

Why? That's because Costco is classified as a Top Tier gasoline retailer. Fuels approved by Top Tier are indeed intended to be top quality, as they meet such a high level of performance that they're on the same level with the standards instituted by major manufacturers. This helps set Costco's fuel apart, as it contains five times the minimum detergent requirement. The company's gas is also filtered to keep water and other debris from contaminating a customer's fuel tank. Costco believes that the end result is fuel that can clean a vehicle's engine and improve its performance.

In addition, Costco's additive-enhanced formula is designed to reduce fuel injector buildup while also helping to improve overall engine operation. When it comes to the grade of fuel Costco sells, the retailer's regular gasoline is typically 87 octane, while premium gasoline is 91 octane. In terms of which one you should use, Costco recommends checking the manufacturer's recommendation for your exact model in the owner's manual.

Costco's claim about the quality of its Top Tier fuels isn't without merit. A study reported by AAA in 2019 conducted on Top Tier and non-Top Tier gasoline revealed some interesting facts. After lab testing both types in a 4,000-mile driving simulation, non-Top Tier fuels left more deposits on each intake valve than Top Tier fuels. In fact, Top Tier had around 95% less deposits than non-Top Tier.

Top Tier has a high-quality standard and Costco can be an easy way to get the gas, but the truth is that some drivers perhaps don't value Top Tier's cleaning ability as much as they value location. According to AAA, 75% of drivers surveyed said that the location of the gas station itself was their way of choosing where to fuel up. Price was the motivating factor for 73% of drivers, and at the bottom of the list, at 12%, were drivers who prioritized detergent additives.

But this could bode well for Costco, as the retail giant has historically offered cheaper gas due, in part, to the revenue it collects from membership fees. In an April 2026 report, CNBC found that Costco's gas prices were cheaper than traditional gas stations in three different cities: Chicago, Rochester, and Los Angeles. Costco was 19 cents less per gallon in Chicago, 20 cents less in Rochester, and 56 cents cheaper in LA, for an average savings of about 37 cents.