To be honest I didn’t see the word “oil” initially, but other comments already addressed this: Walmart does have to deal with large quantities of oil and relate

To be honest I didn’t see the word “oil” initially, but other comments already addressed this: Walmart does have to deal with large quantities of oil and related commodities. In addition to their grocery business, they also run a large logistics operation, and the price of the goods and groceries in their stores at the end of the day doesn’t exclude the cost of their transportation to those stores.