Narrative:

We were flying at FL240 when I noticed that the left engine oil temperature was at red line and the oil pressure had dropped from 50 psi to 25 psi. I notified ATC and requested an immediate landing at twin falls, identification. After being cleared to twin falls, I began a descent in VMC conditions above a broken layer. During the descent I was reviewing the situation and checklists and may have exceeded my descent clearance. The controller was extremely helpful and never mentioned an altitude deviation, but with all that going on in the cockpit, I do not recall each of the descent clrncs. I should have done one of a couple of things: I should either have declared an emergency or taken a deep breath and handled the descent just as any other descent. I purposely did not use the autoplt because if the left engine failed I did not want the aircraft on autoplt. However, I had plenty of time and altitude to do a single engine approach if necessary. I was too anxious to get the airplane on the ground. Events became blurred in the stress of the moment, but there was no reason for that level of stress. I was well trained, current, and had plenty of altitude and an airport within easily reachable distance. The bottom line is that the engine did not fail and the problem was traced to a failed vernatherm.

Google
 

Original NASA ASRS Text

Title: A C421 PLT, DURING CRUISE AT FL240, EXPERIENCED AN ENG PROB, RESULTING IN A DEV TO NEAREST SUITABLE ARPT.

Narrative: WE WERE FLYING AT FL240 WHEN I NOTICED THAT THE L ENG OIL TEMP WAS AT RED LINE AND THE OIL PRESSURE HAD DROPPED FROM 50 PSI TO 25 PSI. I NOTIFIED ATC AND REQUESTED AN IMMEDIATE LNDG AT TWIN FALLS, ID. AFTER BEING CLRED TO TWIN FALLS, I BEGAN A DSCNT IN VMC CONDITIONS ABOVE A BROKEN LAYER. DURING THE DSCNT I WAS REVIEWING THE SIT AND CHKLISTS AND MAY HAVE EXCEEDED MY DSCNT CLRNC. THE CTLR WAS EXTREMELY HELPFUL AND NEVER MENTIONED AN ALTDEV, BUT WITH ALL THAT GOING ON IN THE COCKPIT, I DO NOT RECALL EACH OF THE DSCNT CLRNCS. I SHOULD HAVE DONE ONE OF A COUPLE OF THINGS: I SHOULD EITHER HAVE DECLARED AN EMER OR TAKEN A DEEP BREATH AND HANDLED THE DSCNT JUST AS ANY OTHER DSCNT. I PURPOSELY DID NOT USE THE AUTOPLT BECAUSE IF THE L ENG FAILED I DID NOT WANT THE ACFT ON AUTOPLT. HOWEVER, I HAD PLENTY OF TIME AND ALT TO DO A SINGLE ENG APCH IF NECESSARY. I WAS TOO ANXIOUS TO GET THE AIRPLANE ON THE GND. EVENTS BECAME BLURRED IN THE STRESS OF THE MOMENT, BUT THERE WAS NO REASON FOR THAT LEVEL OF STRESS. I WAS WELL TRAINED, CURRENT, AND HAD PLENTY OF ALT AND AN ARPT WITHIN EASILY REACHABLE DISTANCE. THE BOTTOM LINE IS THAT THE ENG DID NOT FAIL AND THE PROB WAS TRACED TO A FAILED VERNATHERM.

Data retrieved from NASA's ASRS site as of July 2007 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.