PA-31 pilot reported loss of oil pressure in right engine during cruise. Pilot performed inflight shutdown and diverted to safe landing.

Narrative

Two flights were planned for today. The first was a VFR to IFR flight out of ZZZZ with just myself on board to ZZZZ1. The second was a IFR return to ZZZZ with two passengers on board. The flight was a private flight on behalf of the aircraft owner operating under Part 91 of the FAR's. After updating the aircraft database I did a pre-flight of the aircraft. Oil was checked and deemed satisfactory for the series of flights for the day. This was verified with tech log entries showing recent addition of oil in each engine. The flight to ZZZZ1 was uneventful. During the flight I made a mental note that the right engine oil was reading high; but just within limits. Oil pressure was consistently in the 'green'. On the return flight; all engine parameters were indicating as before; until I was north of City X. During my routine 'scan' I noticed a decline in the right engine oil pressure gauge. Over the next 10 minutes the decline was continuing; with the Oil temperature reading off the scale. As the oil pressure further dropped I elected to deliberately shut down the right engine as a precaution. Just before executing the procedure I was handed over to 'ZZZZ Control' on XXX.XXX and I advised them of my intentions to shut down the right engine due to a low oil pressure indication. Given my altitude at FL100 and my track distance to ZZZZ2 I initially asked for a vector to ZZZZ2. I informed my passengers of the precautionary action I was about to take; then I shut down the right engine. Once the engine was secured I evaluated my diversion and elected to divert to ZZZZ2 as it would give me sufficient time to drift down and run all my checks and plan my approach. The weather was VMC conditions. The remainder of the flight was uneventful; and after taking care of the passengers and securing the aircraft; I notified maintenance and began submitting my safety reports whilst everything was fresh in my memory. There was no injury to person or damage to aircraft or property.