Pilot reported Oil Pressure began to rise steadily during cruise. Pilot diverted and made a precautionary landing.

Narrative

This report is regarding a VFR General Aviation flight that took place on Day 1. The Pilot in Command was Person A; Aircraft X. Two souls were on board the aircraft. The origin of this flight took place at ZZZ. The departure time was XA00 UTC on Runway XX. The intended destination was ZZZ1 airport.The first leg of the flight was completed successfully; and the touchdown occurred at XA44 UTC using Runway XX. Departure from ZZZ1 took place at XB36 UTC from Runway XX. Aircraft X departed with 2 souls on board and 48 gallons of 100LL Avgas. Clearance was issued to enter the ZZZ2 airspace by ZZZ Approach at 2000 ft. southbound. By the time the aircraft reached ZZZ3; the oil pressure gauge began entering the yellow arch. As a safety precaution; a request was made to the ZZZ4 Tower for a higher altitude when crossing the large area of water following ZZZ5. ZZZ4 Tower initially asked if any assistance was needed. This was declined at the time. However; souls on board and fuel remaining were requested. After being handed off to the ZZZ Approach; permission to climb to 4;500 feet was granted; followed by permission to climb to 6;500 feet. Finally; the pilot's discretion was given for altitude. This; however; was shortly followed by a request for landing. ZZZ6 was offered; about 30 miles north of the aircraft's current location. This was declined; as crossing the water with unknown engine trouble was unfavorable. ZZZ7 and ZZZ8 were then offered. ZZZ7 was chosen; and a left turn was made toward the field. This airport was chosen; as it was known that ZZZ8 has a short Runway; poor lighting; and a congested area nearby with fuel tanks. ZZZ7 was determined to be the safest option. During the turn to the airport; the oil pressure gauge dangerously entered the red; indicating excessively high pressure. [Priority handling was requested]; and instructions to expect Runway XXR at ZZZ7 were given. A descent was made from 5;500 feet; and at XC24 UTC; a successful landing was made on Runway XXR at ZZZ7. Upon exiting the Runway; Aircraft X's engine was shut down on the Taxiway; and the passengers exited the aircraft. Fire rescue was on standby during touchdown. During this time; ZZZ7's in-use Runways were XYL and XYR. The aircraft was then towed from the Taxiway and currently resides at FBO on the field.