QUESTION: I have a 1968 Mooney-F with an IO-360-A1A. The oil cooler was relocated to the J model position with an STC and the cowl openings have been changed to the J-model size. I have sustained oil temperatures of 206°-210° when leaned to 100° rich of peak and will reach 215°-220° if leaned to 75° rich. What is the maximum oil temperature that this engine should run?
I have replaced the baffles and plugged any holes in the shroud. The engine has 25 hours SMOH with a replaced case, new cylinders, new vernatherm, the vernatherm seat reground, new oil lines and oil cooler. Any suggestions?
ANSWER: I don’t think you have anything to be excited about providing you can verify a few things. What you may be seeing with your oil temperature is a result of two separate things. If you had the cowl modification done at the same time as having your engine overhauled, it could be a combination of both. Either or both of these changes to your aircraft may have an influence on the oil temperature. The engine may be running a little warmer due to the closer tolerances as a result of the overhaul. The modification to the airflow to and from the oil cooler by the cowl modification also may have some impact.
If you are confident in the accuracy of your instruments, I’d still not be too concerned with an oil temperature of 210°F or a bit higher in climb. The maximum continuous oil temperature for your specific engine is 245°F.
I’d suggest you continue to keep an eye on the oil temperature and see if it becomes hotter with the summer weather. You didn’t mention anything about cylinder head temperatures, so I assume they are OK? If they might be a little hotter, it also can be a result of the things mentioned before or maybe the mag to engine timing should be rechecked just in case it may be off just a little. That could cause higher CHT and also drag the oil temperature up.
Again, I don’t think you’ve got anything serious to worry about, but just keep notes of each flight and I expect you should see a reduction in temperatures as you put time on it.
Paul McBride, recognized worldwide as an expert on engines, retired after almost 40 years with Lycoming. Send your questions to: AskPaul@GeneralAviationNews.com.