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Originally Posted by M-technik-3  For a M44 and M/S 5X zinc is not needed, it actually harms the cat converter. I have used diesel oil in my S52 but that was to quiet a loud lifter. |
1 or 2 cycles doesn't hurt the cat a bit and the cam still needs zinc to surface harden correctly.. IF your using a new cam and new lifters/followers every place metal rubs on metal break in oil will help the motor break in without flattening/galling the lobes, its even more critical on the M42 without lifters..
Ive worked on dozens of race motors and its night and day difference how the cams look after run-in..