"The pressure relief valve is what regulates engine oil pressure. It's a simple device consisting of a spring-loaded plunger that is designed to open when oil pressure reaches a certain level (typically about 50 psi for Continentals and 70 psi for Lycomings) to bypass excess pressure from the pump."

https://www.aopa.org/news-and-media/all-news/2019/december/pilot/savvy-maintenance-hostage-situation