What is the oily stuff all over new Motorcraft master cylinder reservoir caps?

Sep 5, 2017
I bought a new master cylinder cap online and thought it might have been tampered with when I saw all this oily stuff on it in the package (see the attached picture). So, I ordered another one from a different source, but it was covered in oily stuff too.

Does anyone know what this stuff is and what its purpose is?


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Probably keeps the rubber from drying out
I thought the same thing. But I think the gasket is silicone, and I've never known silicone to dry out in any resonable period of time. Maybe they wanted to make these shelf-stable for 20 years, though. The ones I received were packaged in 2015 and 2018, so I guess they do sit around on the shelf for prolonged times.
P80 assembly lubricant?

P-80® IFC THIX is a Biodegradable Gel Temporary Assembly Lubricant for Incidental Food Contact (IFC) eases installation of tight-fitting rubber and plastic parts by reducing the force needed for assembly especially useful in overhead and vertical assembly operations because it remains where it is applied without dripping. Once assembly is complete, the lubricant dries and the part returns to its original condition. Will not become slippery again, even in the presence of moisture. Does not contain silicone, alcohol, or petroleum distillates. Safe for use on most natural and synthetic rubbers, metals and plastics and safe for workers and the environment.

Used to temporarily lubricate pump seals, hoses, o-rings, bushings, gaskets, grommets, grips, and many other rubber and plastic parts.