my low oil presure light comes on at one of two times. if the jeep is at a low idle or when i am coming to a slow stop, once i start driving the light goes off. and stays off till i come to a stop. I just changed the oil 1300 miles ago used castrol synblend 5-30 and a normal fram filter. there seems to be no loss in h.p. what could be causing the problem and where should i start? thanks.