The rule of thumb from the mechanic's school of wisdom is any time u have an oil warning light showing fault you must Dx the prob ASAP and the first Dx tool in this case is a good mechanical oil pressure gauge.
All VWs after some point in the late 80s have a "dynamic oil pressure monitoring sys". Basically this involves 2 oil pressure switches, one low (0.3-0.15 bar) and one "high" (1.15-1:08 bar) along with some circuitry monitoring RPMs. The principle is two fold and simple:
1) alert user when the eng has oil press below the press. of the low sensor; warning light is illuminated solid.
2) alert the user when the oil pressure at a pre set RPM (1800rpm for instance) dips below a pre determined level. Oil light flashes, and in some models an audible alarm is sounded.
This is a rough generalization from memory up through the A3 model yrs (99), and later models use a similar but more advanced system of alerting the driver.
So, that's how the system works. First step is to always check the oil pressure with a mechanical gauge
1) at idle and full operating temp FOT (87* C);
2) at FOT at idle, 1000rpm, 1500rpm, 2000rpm, etc.
Compare the results with the min OP found in the Bentley manuals.
Cold start oil pressures mean almost nothing so don't get lured into false good news by only checking that!
Ok VW mech school is jetzt geschlossen :-)
Justin
2000 EVW 5-spd TDI