Volkswagen Repair: Oil Light, oil pressure guage, vw golf 1

Question
1994  VW Golf 1.8L Gas. 225000km. Properly cared for.
When driving after the engine warms up and at certain rev ranges (no tach)75-80km/hr in 5th, similar ranges in other gears, the oil light and buzzer come on. Changing speed stops it as does reving the engine a little. No oil leaks, level OK regular changes and filters etc...I'm baffled and unsure what is going on. Like to have some possible ideas before taking it to the shop. Any help would be greatly appreciated.

Chris Nordland

Answer
It's letting you know that the oil pressure has dropped below preset  SO either the sensor is faulty,  or the oil yourusing is too thin.  I would dothefollowing.  First, clean the sensor connection on the head where the wire connects with some sandpaper and reattach making sure the wire connector sides on firmly.  Second,or third...replace the oil with thicker say 20/50 or the sensor to see if that is the problem.  Other than that a oil pressure guage should be hooked up to see what the pressure is.  Definitely a concern.