oil light comes on on tickover vauxhall vectra dti?

Other possibilities are-

wrong grade/poor quality of oil
oil not been changed in line with service schedule

has also been known for diesel to leak into the crank case and dilute the oil, have you been checking the oil level regularly, is it rising, does it smell of diesel?

dan
March 2010

Might be one of the following
Engine low on oil
Faulty oil pressure switch
Wrong type of oil filter - None return valve faulty missing
Engine oil pump worn out
Worn bearings

Maurice
March 2010