low oil pressure

I'm new to these but I brought a new one home yesterday and it seems that the oil pressure seems to be reading on the low side. Like I said, I'm new to this vehicle so I can't tell what is "normal" for it. But I seem to read that this may be an ongoing issue for this engine and some models...

My oil pressure is reading low. I changed out the oil pressure sending unit and it still reads low. I attached a presure gauage where the sending unit goes and and reads 40psi while ideling but still nothing on the dash. Anyone have any ideas?