I just changed my oil, with Mobil 1 synthetic as usual and was wondering why all of a sudden my oil light goes on when my car gets warm, the oil light only goes on at idle, but my idle drops to a steady 650rpm instead of the usual 750rpm, when I rev it up just a tad the oil light diminishes .... is this a serious problem what could be the cause of it?

Thnx

Marko
license [AWD TSI]