2 adjectives to describe lubricators

The thyroid, therefore, in addition to its rôle as an accelerator, acts, too, as the efficient lubricator for energy transformations.

Some natures are antagonized by the shadow of a threat, even if it accompanies a reasonable order; and if we acknowledge that the oil of courtesy is a valuable lubricator in our dealings with grown people, it seems proper to suppose that it would not be entirely useless with children.

2 adjectives to describe  lubricators