Synthetic oil used to be something only performance cars needed, but not anymore. Now it’s the manufacturer-recommended engine lubricant in many mainstream vehicles, such as the Subaru Forester ...

which directly compete with the big names in the motor oil game, like Mobil 1 and Valvoline. Such competition, of course, ...

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 ...