I have a 2002 Ford Taurus with 145K 3.0 Vulcan V6. Last couple of years oil light will come On or flicker at idle on a warm to hot day. Only after oil changes. First time It came on no knocking so I changed sending unit still came on. Put a manual gage on it and pressure was down between 5 and 10 at idle. But as the oil ages and gets dirty the light comes on less and by the time its due for another change and the oil is dirty it doesn’t come on at all. Next time oil is changed starts same process. Car runs great, has some slight blowby. Was wonder if this is kinda same principle as a transmission? Dirty fluid or in this case oil have more friction or resistance?
Engine is worn out. Nothing much to lose at this point, you can try a heavier oil or some Lucas oil stabilizer.
As oil wears out (gets "cooked" by heat), it becomes thicker. Then it's like trying to blow honey through a straw (the pressure in your mouth increases) versus water.