fd56ec0a_MOTOR_OIL_GUIDE__Use___Definition
[API Symbol] CB (obsolete) (Moderate Duty Diesel Engine Service) [Use & Definition] 
Service typical of diesel engines operated in mild to moderate duty, but with lower quality fuels which necessitate more protection from wear and deposits. Occasionally has included gasoline engines in mild service. Oils designed for this service were introduced in 1949. Such oils provide necessary protection from bearing corrosion and from high temperature deposits in normally aspirated diesel engines with higher sulfur fuels.
MOTOR OIL GUIDE
Use & Definition