Even the most disciplined stewards of consumer value eventually meet the limits of what they can absorb. Costco — long regarded as a bulwark against the creeping tide of retail inflation — has quietly raised prices on its Kirkland-brand motor oil and placed caps on how much any single member may purchase, a pairing of signals that points to genuine strain somewhere in the supply chain behind one of America's most trusted private-label products. The move is small in isolation, but in the language of warehouse retail, where price stability is a covenant with the customer, it carries the weight o