Gaining a good understanding of your car's motor oil is crucial to ensuring it runs properly. If you're a Costco member, you may have come across the chain's exclusive Kirkland Signature Synthetic ...

Costco's store brand oil, sold under the ... Royal Purple's motor oils, most of which are fully synthetic, are known for their high quality, good reputation, and purple color.

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 ...