was it a drastic change.. like one day was 60, the next 30?
if so.. was it after a service event. like oil / filter change?
always investigave drastic changes and try to determine if you just did something that may contribute to it... pinced off a cap line.. different oil.. different filter.. etc.
lastly. i always keep a reference oil gauge handy to double check. I also change out oil pressure gauges whhen i get a tractor. gauges DO go bad. I have seen 4-30 psi difference on a replaced gauge vs one installed when i got it.
also.. is this a gasser or diesel?
original engine ( casting codes ) ?
oil and filter type?