Costco gas is known for its high quality and affordability. It meets Top Tier™ standards, containing advanced detergents that help keep engines clean and improve performance. Costco sources fuel from major refineries and rigorously tests it for consistency. While it's typically cheaper than competitors, membership is required to access Costco gas stations.

https://www.savingadvice.com/articles/2025/02/12/1022458_costco-gas-quality.html