oil warning light is not for checking oil level, it is there to check that there is oil pressure to lube crank/cams etc.....if it is going on/off the wire to oil pressure sender could be shorting to earth,you will need to locate sender and follow wire from it hoping that you can find fault,it could also be faulty-you may need to get oil pressure checked by independant gauge at local garage to rule out oil pump fault!
k
March 2009