make a long story short got a used es300 for my newbie driving daughter with 140 k . I'm going thru the car myself and replaced battery, sway bar link, belts, power steering hose and rebuilt power steering pump. Since the engine is a known sludger I put in M1 5/30 high mileage to slowly clean motor. Engine runs like swiss watch. I drive it for a couple weeks to make sure everything is ok. I notice after I exit the highway at idle at stoplight. Oil pressure light pops on for a second. I put in neutral and it goes out. I go home and remove oil sender. Sender is new and had been recently changed. I change sender again as I didn't have a 90 fitting for my pressure tester. Light still flickers after a highway run at idle. So I think I found out why car was sold. Knowing this engine was a known sludger I drain oil and drop pan. There is some varnish only. I remove oil pump and inspect it. the screen is 75% clogged. I start cleaning the screen and realize it is not sludge, I am removing rubber. i then find a circular piece of rubber on the screen. It is the darn pvc grommet. Someone replaced pvc and grommet. Old grommet must have fallen into valve cover where it melted into the oil and congealed on the oil pump screen. put it all back together and drove it for a week and no issues. So if you have low oil pressure always drop the pan and check the pick up screen for debris and the oil pump bolts are tight. The old 740's were known to loosen there pump bolts and cause low oil pressure grenading engines.