The TEOST 33C test (ASTM D6335) is an industry standard bench test that simulates turbocharger operating conditions. According to the American Society for Testing and Materials (ASTM), it is “designed to predict the high temperature deposit forming tendencies of an engine oil.” To meet the API SN Resource Conserving and ILSAC GF-5 motor oil specifications that are often recommended by vehicle manufacturers, a 5W- 30 motor oil must limit total deposit formation to 30 mg or less.