With 235k miles on the original engine with this "knock" from new, I don't understand the concern. If is truly a knock, it would not be related to the oil supply, but pre-detonation. What grade fuel are you using? Have you checked/cleaned/replaced the knock sensors? Most vehicles with knock sensors will knock momentarily at start-up because the sensor does not yet have a signal to respond to. But, with 235k miles, I don't understand the concern.