First, are you sure it's the oil light?
Secondly, the oil light is a warning of low oil PRESSURE, NOT low oil level. Dont overfill it, you'll cause even more problems.
Change the oil and filter. Make sure you use the correct grade of oil, best to buy it and filter from Vauxhall dealer spares dept.
If that doesn't sort it you may have a faulty pressure sensor/switch. Either fit a new sensor or get the pressure tested.
If the pressure is low you may have a faulty pump, worn main bearings or a blocked oil pick-up strainer.
setter
July 2009