Narrative:

During cruise at FL190; noticed that the oil pressure on the right engine was lower than usual; the cylinder head temperature was a little higher than usual. The engine monitor looked normal. Continued to monitor closely. Just to the east of the ZZZ airport; noticed that the oil pressure started to drop. Adjusted the mixture slightly to add fuel and cool the engine; the engine coughed slightly.although I was only 20 minutes from my destination; I was unable to ascertain the weather - the ceiling was not reporting and the surrounding reports were MVFR. Decided to change destination to ZZZ1 which was in sight and clearly VFR. Requested center to change destination to ZZZ1.during the decent; I gently pulled the manifold pressure back to normal approach setting of 25 inches - the oil pressure dropped to 50 psi (approximately 50% of normal). Upon beginning the approach the engine was continuing to produce power and there were no other indications of a problem. I asked the tower if they knew if the airport fbos had an engine shop. They replied that they had no information.because the engines on the duke are unique; and the engine was now stable and producing power; I decided to return to my original destination where service could be performed. I continued VFR below the cloud cover and landed normally without further incident. Upon inspection after landing; the engine cowling had significant oil on the outside. At this time; the mechanic is beginning the investigation as to the cause.

Related reports:

Google
 

Original NASA ASRS Text

Title: After originally diverting to a nearby airport; the pilot of a BE60 opted to continue to his destination when initial concerns regarding the right engine oil pressure abated.

Narrative: During cruise at FL190; noticed that the oil pressure on the right engine was lower than usual; the cylinder head temperature was a little higher than usual. The engine monitor looked normal. Continued to monitor closely. Just to the east of the ZZZ airport; noticed that the oil pressure started to drop. Adjusted the mixture slightly to add fuel and cool the engine; the engine coughed slightly.Although I was only 20 minutes from my destination; I was unable to ascertain the weather - the ceiling was not reporting and the surrounding reports were MVFR. Decided to change destination to ZZZ1 which was in sight and clearly VFR. Requested center to change destination to ZZZ1.During the decent; I gently pulled the manifold pressure back to normal approach setting of 25 inches - the oil pressure dropped to 50 PSI (approximately 50% of normal). Upon beginning the approach the engine was continuing to produce power and there were no other indications of a problem. I asked the Tower if they knew if the airport FBOs had an engine shop. They replied that they had no information.Because the engines on the Duke are unique; and the engine was now stable and producing power; I decided to return to my original destination where service could be performed. I continued VFR below the cloud cover and landed normally without further incident. Upon inspection after landing; the engine cowling had significant oil on the outside. At this time; the mechanic is beginning the investigation as to the cause.

Data retrieved from NASA's ASRS site as of April 2012 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.