Costco has seen unprecedented demand for gas as prices surged above $4 nationwide and $6 on the West Coast.

The retailer undercuts local gas stations by around 30 cents a gallon by relying on membership fees for profit.

About half of customers who fill up at Costco gas stations end up shopping in the warehouse.

AI-generated summary was reviewed by a CNN editor.

In its 50-year history, Costco has never seen such demand for gas.