BMW Repair: Oil Pressure Light and Read Out, oil pressure gauge, engine oil pressure

Question
My 1989 735il had the oil pressure sensor replaced last year.  After the car runs awile, the oil light and read out "engine oil pressure" appears, but just at idle (which is set just below 1 on the tach).  When I give it any gas and take off, the light and read out disappear.  My performance is not affected in the least.  How can I defeat this light and read out coming on?  

p.s.  what grade of fuel is best for my 3.5l engine.   I am currently using mid grade 89 octane.  Is this a good choice?

Answer
The best way to go about diagnoseing this problem is to determine if the idiot light is acurate or if it's a wireing problem.
Get an oil pressure gauge and idle the engine with it plugged in to see how low it really is.  if it's in fact within spec. the wireing or the sensor are at fault.
-cheers

I'm not sure off hand what fuel is recomended for your engine though i do know it says in the owners manual.