Pontiac Repair: Oil pressure on 3.8l turbo pontiac bonn. ssei, factory oil, oil pressure

Question
My Pontiac has about 160k on it when first started it rattles a bit like lifters but quickly stops within seconds as it it was slow getting oiled, then once warmed up if you come to an idle the oil pressure drops below 10psi and engine light comes on, but it holds a good 50+ on pressure with even the slightest increase in rpm. have been told after getting it looked at that with a gauge it reads fine oil pressure ..but  with the first crank rattle and the fact that these problems seem to be much more noticeable in hot summer than cold winter i cant help but wonder if i do have an oil pressure issue any ideas on this?

Answer
Well shane:

With 160K on that engine I'm sure it needs some work. I'm sure it has wear and it's loosing oil pressure. I looked up specs for a 99 sisnce you didn't tell me what year this is but engine at operating temp and running at 1875 rpm's it should have a minimum of 60 PSI there is no spec for hot at Idle. My guess is that it's too low. Your more than likely looking at having to get this engine freshened up. As for the noise at start up make sure you re using a factory oil filter it has a check valve in it to keep the oil in the top half of the engine when it's shut off. If you start to experince any loud knocking noises do not drive it and get it fixed sooner rather than later. Good luck :)