Costco's Kirkland Motor Oil is available ... it nearly 6,000 reviews and a 5 star rating on their own store site. You'll find a gallon of AMSOIL (AMSOIL Signature Series 5W-30 Synthetic) available ...

Those shopping at Costco may have encountered the chain’s exclusive Kirkland Signature Synthetic Motor Oil and wondered how it compares to some of the best motor oil brands. While the brand is ...