Maybe your oil pump is a little slow, perhaps get a new pump. As long as it doesnt come on any time when you are driving it should be ok. My van does the same. Perhaps use a thinner oil?
im no mechanic though
What oil did you use to "fill every orrifice"? Some cars can be fairly fussy about what oil you use. I woudl automatically look at the oil pump if the car has a few km on the clock. If not it might be time for a service... think of it as an xmas present for your car