Workhorse 8.1L Low Oil Pressure

With your Actia dash you can program it to give you your oil pressure reading. Mine used to run about 45 psi at normal cruise and drop down to 15 psi or so at idle.
As mentioned, the Actia dash sometimes will go crazy. To reset mine I just flipped the chassis battery disconnect switch.

Sounds like your oil pump is sucking air when the oil runs to the back of the sump ... maybe your oil pick up tube has a pin hole?

Are you low on oil?

When was the last time you changed oil and filter? Who did it?

You have the Actia dash gauges and Actia has a known problem of randomly setting off the alarm and all gauges pegging. It then resets itself and all is well. Mine will do it several times a year. Used to scare me half to death, now I just ignore it.

What do you have to do to clear the oil light?

X2 on the above or your oil is cooked or just very, very, cheap.

Could be an oil pressure sending unit or the gauge going bad.