You have to give the American Petroleum Institute, SAE International, and U.S. And Japanese automakers credit. They work hard with industry stakeholders to establish performance standards for engine oil. Once the standards are established, API deserves even more credit for its Engine Oil Licensing and Certification System. This system includes the API Service Symbol and Certification Mark to help consumers identify the optimum engine oil. API also conducts field testing and audits to spot-check quality and claims.