Check owners man for oil light (I don' t recall). Maybe it wasn't low enough to trigger the light. Also, the oil pressure gauge will drop when the oil is hot and less viscous. It should be pegged when the revs are up, but when you stop at light and the motor is hot, it'll drop some. Oil pressure and amount of oil aren't directly correlated. You could have that baby topped off and run at 1.5 bar with the revs up -- eg bad oil pressure.