The invention provides a combined fluid level sight gage and ultrasonic sensor featuring a fluid level sight gage having a housing for containing a fluid and having a sight glass for viewing the level of the fluid therein, and an ultrasonic sensor coupled to the housing, responsive to the level of fluid in the housing, for providing an ultrasonic sensor signal containing information about the level of fluid in the housing. In operation, the sight glass provides a visual verification that the ultrasonic sensor is working correctly in relation to the fluid visible in the sight glass. The ultrasonic sensor signal may be used to automatically annunciate alarms or warnings either locally at the equipment or by wired or wireless electronic means. In some embodiments according to the present invention, the housing has a centerline for indicating a normal fluid level therein. The ultrasonic sensor may be arranged in the housing on the centerline, or slightly below the centerline, or slightly above the centerline.