Originally Posted by dwightdmagee

The system does not measure distance or time, but oil contaminants - the meter measures electrical resistance through the oil supply. Oil alone offers no electrical resistance, but dirt does. As the oil becomes contaminated, the meter measures electrical resistance across the oil supply and does the miles-to-next-change count-down.

Like hwcoleman said, the idiot light indicates low oil pressure/volume. Check this pronto.

Good luck.