"Replace first" is the last thing we want to hear. That is the most expensive and least effective way to solve a problem. You will spend less money and time by having a mechanic diagnose the cause of the problem.
A common cause of an unwarranted "Low Oil Pressure" warning light is a defective sending unit. Often that is accompanied by oil leaking from it. That is a sure clue to replace that sensor. When there is no leakage from it, your mechanic will replace it temporarily with a mechanical gauge to determine if the pressure really is low. If the pressure only drops at higher engine speeds, it is possible the bearings are worn and the oil pump cannot keep up with the internal leakage, but it is more likely there is debris in the oil pan that is blocking the pickup screen. At lower speeds, less oil volume needs to be pumped, and if enough oil can make it through that debris, the pump may be able to maintain enough pressure for the warning light to stay off.
Also, consider that oil gets pumped up to the top of the engine, then has to run down through drain back holes. It runs down at the same rate, regardless of how fast the engine is running. If the engine is full of sludge, those holes can become blocked and impede the draining of the oil. Too much gets hung up on top at higher speeds, and that can result in low oil level in the pan and by the pickup screen. If the pump sucks up air, that can be compressed and prevent pressure from being maintained.
Of course low oil level can also cause low pressure if air gets sucked into the pump. At low engine speeds what little oil is in the engine might drain back to the pan fast enough to keep the pump happy. At higher speeds, oil is pumped to the top of the engine at a faster rate, leaving the pump starved and drawing in air.
Sunday, January 8th, 2017 AT 2:14 PM