Lubricant

Lubricant is a darkish black fluid contained within the body of a transformer that is (presumably) used to make the mechanical joints of a transformer move more smoothly. Lubricant can be excreted from a masculine transformer in a way that is analogous to the way that a male human passes urine. It is unknown how feminine transformers pass lubricant.

It is offensive to transformers to "leak lubricant" on them as implied by [Ironhide]'s near willingness to turn Sam's dog [Mojo] into a smouldering crater just by peeing on him. Although it is offensive to lubricate transformers, it is not seen as offensive (to the transformers) to leak lubricant on humans; especially if [said human] kidnapped insulted the [owner] of the only known way to locate the [lifeforce] of the entire transformer race.