I'm having a problem with the oil gauge, on a 1994 90 quattro with the V6. The light comes on when I am city driving. It comes on for about 2 seconds and goes off again. I have taken it in and the mechanic said it may be thin oil. He changed the oil and it stopped for about 1-2 weeks. It has started again. I am thinking of adding an oil additive to see if that stops it. Any suggestions??