92 318 w150; I am not sure the pressure, but it starts at the first line from the left when its cold and as it warms up it drops alittle

 

well, oil pressure will drop when the car heats up
the oil gets thinner, so pressure drops
how much of a pressure drop occurs?

 

Yep.. oil pressure drops as it warms up..

Running oil something like 20w50 will help increase oil pressure.

Get an aftermarket gauge to see what your oil pressure is in PSI.

 

that was my next step with the gauges. I just thought it started off kinda low

 

At what pressure should i start being concerned

 

If it starts falling under 15 psi when warmed at 1,000 RPM

 

I would use a mechanical gauge to measure the pressure as those are usually more accurate than the electric sending units. Just something that I have noticed over the years.

One thing could be causing the issue is that the oil pump may need to be rebuilt.

 

the general rule is 10lbs per 1000 rpm

 

Have this issue with my 95 318 magnum, 257k miles. Around 180k I started getting low, and fluttering at idle, oil pressure. I've also had a bad head gasket forever[used to foam the oil], but I think it sealed itself by now! Changed the oil pump at about 230k, no joy. Saw anti-freeze dripping from one of the cylinders and off the crank, oh well. Since then I have been using the Lucas oil treatment or 20w-50 to maintain oil pressure. Yeah, just a band aid, but at this point no sense in rebuilding it. I'll just wait till it blows and toss in another used 5.2, they made a gazillion of them, not hard or expensive to find.