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Q: Low warm oil pressure. New oil.

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New oil and filter. New pressure sensor. Once engine warms oil pressure bottoms out and oil light comes on. What could this be.

My car has 124000 miles.
My car has an automatic transmission.

A: Hi. In order for any liquid to have pressur...

Hi. In order for any liquid to have pressure, there has to be a restriction. The restriction in an engine is the oil clearance on the rotating parts. On a newer engine, it is roughly 0.0015 of one inch. This is the area that there is a pressurized film of oil that the crankshaft, rods, and camshaft ride on. As the engine parts and oil pump wear, the gap becomes larger and oil pressure is reduced. Oil pressure on every engine is at its lowest at idle and when hot.

Here are a few things to try. Install a Nissan oil filter. Some aftermarket ones are much smaller than the original and restrict flow. Double check the weight of the oil recommended in your owner's manual. Using a thinner oil will reduce oil pressure. The higher the number, the thicker the oil.

Ok, you tried all the easy stuff. Now we have to dig into the engine. Install an oil pressure gauge to verify the actual pressure. Next, remove the oil pan to look for a clogged oil pickup screen. At this point you could remove a main bearing cap, or all of them, to look for an issue. The general condition of the engine can be physically seen at this point. The only way to inspect the oil pump is to remove it and take it apart. If the screen wasn't clogged, and the accessible bearings measure ok, it's time to replace the pump. If a new pump did not correct the issue, the engine will need rebuilt or replaced.

Your could try using thicker oil if the car is not worth any investment. This could have some negative effects on the variable valve timing. If the oil pick up screen is clogged, this will make the problem worse and possibly ruin the engine. If you need further assistance, I recommend you have a certified technician, like one from YourMechanic, inspect the oil light on your vehicle and suggest an appropriate repair.

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