could also be worn crankshaft bearings!you need to get pressure checked with an independant gauge [may be faulty switch?]
k
July 2010
if your oil level is ok then it could be that the oil pump is on its ay out...i had the same problem with my omega and ignored it to my peril (omega now in breakers yard boo ho)
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix cars.