ok first off... this is the stock gauge, so accuracy is questionable. motor has 85 k, all of this started happening 2k miles after cam swap.

cold startup (before cam) used to be like 2/3 on the gauge, then hot idle was 1st tick mark, and it was pretty linear in going up to about the 1/2 way mark when it revved up.

now probably in the last 4 months...

Situation 1: cold startup can be 2/3, or sometime a little less than half. hot idle is still about the 1st tick mark. when the motor revs hot, the needle goes up proportionately but only about 3/8 position.

Situation 2: Funny thing is, after about 500-1k miles on fresh 10w30 mobil 1 the oil pressure is 3/8 cold, 1st tick hot idle, and maybe like 3/8 at high revs sometimes, other times it barely moves from the 1st tick.

still funnier is that when I change my oil and filter (dipstick reads 1/2 way between add and full when cold) the oil pressure goes back to how it was in Situation 1. Then after 500-1k miles, it goes back to Situation #2. this is pretty repeatable cuz the last 3 oil changes it has been doing this, and never after it goes to Situation 2, does it ever improve to Situation 1 unless I change the oil. if I add oil it doesn't do jack, one time it made the oil pressure worse.

Oil level is monitored regularly, usually its right around the 1/2 way mark, never overfilled, never too low. OK GUYS! solve my problem

 

I have a similar problem: oil pressure is normal everywhere, except when the car is hot and the temp guage gets to abou the halfway mark.

From there, cooling fans don't come on, but engine continues to get hot, and oil pressure drops lower and lower - until I rev the engine. THen the oil pressure jumps right back up to normal.

I'm about 90% sure that my coolant temp gauge and my oil pressure guage have their wires crossed, perhaps with something else. I'm not sure if this will be your solution, but it's something to consider.

 

ttt

 

problem solved by replacing the oil pressure sensor for $22.68.

after sitting for 2 hours, idle is a tick above 1/2 way marker now probably be just a hair below 1/2 once fully warmed up.