it was topped up to full in May ?
Comments lke this never fail to shock me.  my car hardly uses a drop, but i check the levels and tyre pressure every single time i wash it. 
It takes 20 seconds to do this, and could save you from a whole world of pain. by the time your oil light comes on, there is a good chance that its to late.  

Love you car, and look after it.  
