There is a wide variety of cooking oils from plant sources such as olive oil, palm oil, soybean oil, canola oil (rapeseed oil), corn oil, peanut oil and other vegetable oils, as well as animal-based oils like butter and lard.
We called a couple of the brake fluid companies and the answer was two to five years is a safe number for an unopened container. Wilwoodâs tech line claims that if the container is sealed, they feel it has an unlimited shelf life, but I would consider five years to be the limit.
This is why it is imperative to undergo brake flushing at least once a year and use high quality DOT 3 or DOT 4 brake fluid as recommended by the manufacturer. Consult a trustworthy mechanic for a brake flush service and have your entire braking system checked for proper specifications.