Mechanophilia
A fetish in which the object of desire is a machine, most often a vehicle like a car, motorcycle, or aircraft, and usually written as a romance between a human and a sentient or magically awakened machine. In the stories, the machine has a presence, a voice, or a will of its own, and the intimacy is physical, mechanical, or psychic rather than strictly human.
Readers are drawn to the fantasy of a partner who is powerful, attentive, and utterly devoted, since a sentient machine can be written to read its human lover's needs with impossible precision. The body-horror and body-joy of metal, chrome, and oil also give the sex scenes a texture that no human anatomy offers, which is exactly the novelty the kink is read for.