Okay last night I made this post

So today I go out side with a quart of oil in my hand ready to put it in, but I had the urge to check the oil before. It wasn't low, not even closed to being low... So why did my oil pressure drop like that? Doesn't low oil pressure mean it's low on oil?

 

The pump pulls oil from the pan and pressurizes it. The amount of oil pressure is regulated by the pressure spring in the pump however oil pressure isn't measured at the pump. Oil pressure sensors are mounted in the oil galleries. Oil pressure is fed through the block mainly to oil the mains and rod bearings. If clearances are too great at the bearings then the oil drains out as fast as it can be pumped in and pressure drops. Think of a garden hose. Pressure is constant to the hose but a large opening allows the water to come out quickly reducing the outlet pressure. Putting your thumb over the end of the hose allows pressure to build. The bearings act the same way.

First thing to check is to make sure the gauge is accurate by installing a mechanical gauge into an oil gallery to get a reading.

How many miles are on the oil? Grade? Oil gets very thin when hot and flows out of the bearings quicker.

Change the oil and filter. Cut open the filter. I usually use a hammer and a putty knife to keep any fillings out and cut the base off. Take a section of filter media out and squish it in a vise to get all the oil out. Open up the media and look to see if there's any metal inside. Very, very small flakes are acceptable but lots of metal usually means a bearing is going.

You could have a pump that's on it's way out
You could have an inaccurate gauge
You could have a bad main bearing starting
You could have oil that's lost it's viscosity

 

I probably drove about 100 miles after changing it couple of weeks ago. I used Pennzoil 20w50(I thought the bearings were bad so I switched to a thicker oil)... With only about 100 miles the oil is already black and I think it's because my motor is bad...burnt valves, rings, #3 cylinder bad, and who knows what else....

 

My V6 has similar indications with oil pressure. Before I had my timing chain replaced (first one in 193,000 miles), oil pressure would read about 17 psi at idle (800 rpm) and close to 60 psi at 2500 rpm, higer if it was cold. Now, after I get the car back, pressure at idle is under 10 psi (but never falls to 0) and about 35 - 40 psi at 2500 rpm (pressure at 180 - 190 degrees). Pressure seems normal until the engine warms up, then falls off. I don't know what grade oil was used when the garage changed it with the timing chain replacement, I was told it was 10W-30, which I use. I took it back and had it looked at, but all they did was check the crankcase full and sent me on my way "good to go." It's coming up time for another oil change soon, I'll do this first, then see what happens. Any comments or ideas appreciated, thank you.