low oil pressure can result in oil starvation and throwing a rod through the oil pan or block.

my 300zx has low oil pressure, and lost of power, slight knocking noise. so i wont even start it until i buy a new oil pump.

 

When I drove today, the gauge stayed at one spot the whole time. Is this a sign the gauge is bad? Does this rule out other things?

 

my oil gauge doesn't move either. i didnt even think it was a PSI gauge, i thought it was just a level gauge.

 

You really need to hook up a mechanical gauge (where it will tell you the specific oil PSI), as I said before. That will be the only way to know for sure what PSI is getting to the engine, and what the PSI difference is between different RPMs.
I would advise to NOT RUN THE MOTOR until you get a mechanical gauge hooked up and you can verify the exact oil pressure. Because, if you are running on very low oil pressure, you WILL damage the motor.
If you hook up a mechanical gauge and everything checks out ok, your next step is to replace the sending unit (the item you had to remove to temporarily install the mechanical gauge)
OR
If the oil pressure is indeed low, just post on here, and we'll post other options.

As far as the oil level gauge, there is no such thing on our trucks. You either have an oil pressure gauge, or a low oil pressure light. There is no low oil level light or low oil level gauge.

 

What about if your oil pressure is in between the 2 low lines at idle, i dont want to find out down the road my engine got F*cked up because of low oil pressure at idle, even if i do swap for a 318 i dont want the 3.9 F*cked up

 

now i know this. usually L/H gauges are low/high. and C/H gauges are cold/hot. and psi gauges have psi printed small somewhere around the logo. the dakota is the first i've seen (that i can remember) that doesn't have psi printed on a pressure gauge.

my work truck has turbo psi, oil psi, water temp, oil temp, and turbo temp gauges. it's a ton of gauges in stock cluster, it's pretty crazy.

 

the 3.9 is fine. nothing to worry about. when my plenum gasket was blown, my oil pressure sat below the half way mark almost all the time. now that its fixed, the oil pressure sits either at the half way line (at idle) or closer to the H side (when driving).