Shop name for the round sight glass threaded into a gearbox, pump bearing housing or compressor crankcase, usually with a center dot or line marking the correct oil level. Some have a reflective back that shows oil dark and air bright. Lube techs read them at every route stop, and a bull's-eye that is cloudy, milky or stained is reason enough to pull a sample.
Heard on the job
Level's right on the dot in the bull's-eye, but it's hazy, pull a sample for water.
Also heard as
- sight glass
- bullseye
- level eye