Knock Out glistened.
He wasn't quite sure what his little pet got out of it all. Humans were, after all, tiny. And Sierra was a fairly small specimen anyway. She was female, and those tended to run small, and her body hadn't quite matured fully besides.
Polishing him to his satisfaction was exhausting even for other Decepticons. For his little human - well. He didn't like to imagine it.
Only that wasn't true. He liked it. He liked the disgusting, smelly perspiration that seeped from her - what were they again? Sweat glands? He liked the way it made her hair cling to her forehead. He liked the grumbling little exhausted gasps that came out of her vocal apparatus. He liked the way her hands slowed down, just enough to be irritating, just when she'd almostgotten it right.
He liked taunting her. "You missed a spot, skin job. I can't be seen anywhere like this." He liked revving his engine suddenly and lurching, knowing she was too fatigued to jump away.
Oh, he never actually hit her. As a rule, he didn't break his toys.
He liked that she knew it. He liked that she'd huff an answer, half-scoffing and half-gasping. "Come on, car. No one else is gonna do this like I do it. The others don't give a - a scrap - about your paint."
She was right, of course. No one else would do it as well. Not without a bribe. He'd stay. She'd laugh, another choked noise, running a free hand futilely through her sweat-damp hair. Then she'd go back to her work, smiling, tight-lipped with concentration.
It amused him, and startled him, and unsettled him, to realize just how much she seemed like one of his own kind at times.
But he couldn't puzzle out why she did it. No Decepticon would put such effort into helping someone else. Humans did that, humans and Autobots. Maybe she just did the things a human did. He didn't like that thought. It disappointed him.
One day, as twilight darkened the sky, every part of him gleaming but one tiny spot on his hood, he couldn't take it any more. "What's in it for you, fleshbag?"
Her hand froze in the middle of the circle it was tracing on his hood. "What do you mean?"
"I mean what the scrap are you doing? I work you until your hydraulics - er, muscles - can barely hold you up."
"You like to look pretty," she said, with a gesture he recognized as half of a shrug.
His engines purred. "I do. But that's not it."
She stared, her eyes widening. Then they narrowed, just the same as Starscream's optics did when he hatched some clever plan. "You go racing," she said. "Whenever you can get away. And you want to look good when you do."
"You knew that already," he answered, waiting.
"I want to race you," she said.
He shuddered, the vibration of his engine making her arm shake and her teeth rattle. "Don't make me kill you, human. You're too amusing for that. It would be a waste."
She smiled. "Take it easy, car. I didn't say I wanted to drive."