Klueber Isoflex 5051

Just use some motor Oil.

The purpose of Lubricating the O-Ring is so that it is able to move and seat properly during the initial installation.

Once the bolts are tight, it serves no purpose.

The O-Ring does the sealing, Not the grease.

Grease allows you to lube the O-Ring Days/Months before installation. Think, Production line.

Oil is just fine if you intend to install the pump within the hour. Think, Workshop.

Yeah, I can’t see paying $200 for a pound of grease.

A friend of mine works on C-130s and they use vaseline. It is compatible with all of the Herc's (many) different types of O-rings.

Parker sells an o-ring lube in a tube and it looks and feels just like Vaseline.