Appreciate the thoughts on this. I wonder if there’s any reason mine would go down a bit more on longer drives? Stepper motor?
You need to understand how oil pressure in an engine is created.
The oil pump, which is driven by the engine and is speed-dependent, generates oil flow, not oil pressure.
This flow of oil is forced through the filter and transported through the oil channels to the bearings. This becomes oil pressure, because at the end of the oil channels in an engine there are usually plain bearings, for example on the camshaft and crankshaft.
The oil is pressed into these plain bearings and can only escape again with difficulty.
This nozzle effect creates back pressure and thus oil pressure.
Now there are several factors that ensure that the oil pressure is no longer the same as with a new engine.
Firstly, if your bearings in the engine are already very worn out, they can no longer hold back the oil, so the oil pressure drops.
As the oil becomes more liquid when it is hot, the oil pressure drops.
When the revolution is low in idle, the pump does not deliver as much flow, so the oil pressure drops.
If you drive for a long time, the oil is of course really hot and everything is really flushed through, so your oil pressure drops to its lowest value when idling then.
But as long as your oil light doesn't come on when idling and the engine has an oil pressure that is close to the middle (40psi) of the instrument display under normal load, everything is fine.