Kirkland motor oil, sold primarily at Costco, is manufactured by Warren Distribution, Inc. This company produces the Kirkland Signature Full Synthetic Motor Oil and also supplies motor oils for other brands such as Walmart's Super Tech and Amazon Basics

. Warren Distribution specializes in lubricants and chemicals and operates mainly in wholesale markets, providing oils that meet industry standards like API SP and ILSAC GF-6A

. Costco does not manufacture the oil itself but contracts Warren Distribution to produce it under the Kirkland brand, allowing Costco to offer it at a competitive price by avoiding heavy marketing costs typical of major oil brands

. Kirkland motor oil is generally well-regarded for its quality and performance, comparable to other value brands made by Warren, though it may not match the advanced formulations of premium oils designed for high- performance or diesel engines

. In summary, Kirkland motor oil is made by Warren Distribution, Inc., a manufacturer known for producing quality synthetic oils for multiple retail brands, with Costco distributing it under the Kirkland Signature label