Bolens Kohler engine problem

[Anonymous Poster]

I have a Bolens HT-20 with a Kohler engine that has the strangest oil pressure problem. When the engine is cold the pressure is 50#. When the engine warms up and is at full throttle it drops to 25#. If I then return the hot engine to idle the oil pressure goes back up to 50#. Normally a slow running engine would have lower pressure and the pressure would increase with the higher RPM. It is a mechanical gauge with a tube. Changed oil to premium 30 wt and put on a new Kohler oil filter and nothing changes. What is wrong? or is just a fluke of the Kohler engines? It is a Kohler model 532 engine. thanks