I have a 2000 c230k 73k miles - oil light is going on around 3500 rpm (80-90 mph). If I back off, the light goes off around 70 mph. Similarly, if I put her in neutral, the light goes off. Oil level is o.k. - not too high or low.

Could this be a bad sensor? Does the sensor measure oil pressure (which would suggest I'm losing pressure)? Could the oil filler cap be losing pressure at high rpms?

Help. Thanks