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Wondering if anyone else has seen this or has an understanding of the issue... I had removed the cowl on my '68 M20F to do an oil and filter change. Fortunately I was dawdling and in no particular hurry to complete this awkward and messy job. I gave my engine a good lookover and noticed that the firesleeve over one of the lines going to the oil cooler was torn open at one point. How could that happen? Then I noticed the culprit. There is a SCAT hose feeding the heater shroud running near this oil line with about an inch of clearance. It appears the oil hose has been beating against the SCAT hose for a long time, presumably due to vibration. The spiral wire in the SCAT hose had broken, leaving two polished and needle-sharp ends pointing at the oil line. These dug through the firesleeve. The only thing preventing the wire ends from chewing their way rapidly through the oil line itself was the steel braid armor over the oil line. One strand of the armor was indeed broken, not enough to permit a puncture, but obviously it was only a matter of time. I normally don't give much thought to SCAT hoses. In the future, I will. Needless to day, I took it straight in to my A&P to have the oil line and SCAT hose replaced. My question is: does the vibrating oil line signify anything serious? Or does it simply need to be tied down better? Oil pressure is totally normal and the gauge doesn't indicate any vibration. The oil cooler on this F-model is in the original location on the cowl and has not been relocated J-style.