Detroit repair-shop owner Ali Alhumaidi noticed a new habit from his customers in recent weeks: They have started bringing in their own motor oil when they need oil changes.

“You tell the customer, with labor, it’s around $100. That’s a lot for an oil change,” Alhumaidi said. Customers are often carrying in bottles of motor oil from Walmart, so Alhumaidi only charges them about $20 to $50 for labor costs.

Higher gas prices are just the warm-up act for drivers, repair shops and retailers like Walmart and Costco.