[dlcarrier]

Fun fact: Costco is TOP TIER approved (https://www.toptiergas.com/gasoline-brands/), just like Marathon, Valero, ExxonMobil, Phillips 66, Chevron, Citgo, Sinckair, and BP.

Also, the rest of those companies refine most of the gasoline in the US, and while they have their own gas stations, they also sell to other gas stations, and their fuel is just as clean, because the EPA requires it to be so, as has has been the case for decades.

Any mixtures need to be specifically tested and approved. The gasoline market it so heavily regulated and consolidated that you can't get better or worse gas by switching suppliers, because there's pretty much no difference, other than regional variations mandated by local regulation.

[jqpabc123]

because the EPA requires it to be so, as has has been the case for decades.

The EPA's concern is the environment --- not your engine.

[dlcarrier]

Fun fact: The better an engine is running, the less it pollutes.