The rule is, only 10 psi per 1,000 RPM is enough to run. However, if you get that low, you are experiening a serious problem in the motor.
How many miles? Any major work to the motor?
The sending unit is famous for reading wrong as well.
However, 28 PSI at idle when the engine is hot....is fine. You will always see more pressure when the engine is cold, and at higher RPM.
Sounds like you are in good shape at 28.
As far as adding oil.....if you are leaking it out, and know it via the large puddle it accumulates in your garage, then that sounds about right. You could have a bad valve cover gasket, rear main, etc. If there are no puddles under the car where you park it, then you are burning the oil through the rings or valve stem seals. So....does it puff a big blue cloud when you first fire it up cold, or trail a faint blue smoke running down the road?
