A good friend of mine with a 328 has noticed a wide fluctuation of reading on his oil pressure gauge. At one point, in a turn, the needle went to a zero reading and the oil pressure light came on momentarily. Shortly thereafter, the needle jumped to the normal operatimg reading and the light went out. He noted that the gauge has been reading erratically recently, but the light only came on that one time.The oil level was 1.5 qts down. Do the gauge and light have separate senders? If this indicates a true drop in oil pressure , what would the causes be? What tests can be run to evaluate this situation?