Warnings: Sticky, voeyeurism/exhibitionsim, crossfaction, self service.
Knock Out had promised himself to break the habit of racing.
After the punishment from Starscream... He shivered at the memory. He could still feel the scratch on his finish. Tracing his fingers over where the scratch used to be, he felt his engine rev in distaste.
The no racing rule had its plusses, like not getting onto Starscream's bad side, but it had one decisive flaw: Since he had no way to expel all the energy building inside him, his systems were high-strung and every little sensation seemed to rev his engine more than ever.
It was driving him nuts.
If he had made this promise to just anyone, he wouldn't care, but he had promised it to himself, and such promises he was determined to keep. But still he had a charge to dispel, and the Nemesis was not a good place to do it. Leaving Breakdown in charge of the med-bay, he went to earth.
The late hour and cold were keeping humans inside. He drove through the empty streets, unnoticed. All around there were cars parked; some of them really, really nice, like that white Porsche, all sleek and well buffed. Knock Out really wasn't sure what it said about him that he was ogling the non-sentient machines, but one would have to be stupid not to appreciate all the eye-candy around.
He searched for a place where he could transform and fantasize about all the beauties. Maybe some wall to lean on, somewhere smelling with oil and petrol and... Oh.
He stopped in front of an old, closed workshop, large enough to host his form in vertical position. He stepped inside, and found something he didn't expect.
Covered with a tarp, which he promptly pulled down, was a beautiful semi.
Knock Out had not tried to reason why and how it got inside, only that it was there, waiting for him.
He transformed and let his fingers brush over the slightly dusty finish. It could use some buffing, but other than that it was perfect. It was so similar to this impressive Autobot truck he had met…
Knock Out smiled.
"Aren't you gorgeous?" He slid his fingers over the wheel-wells, and let them skim over the rubber of the wheel itself.
"Hope you don't mind me... using you a bit, pretty." What was wrong with some fantasies, after all? They often gave the edge that a mech needed to make pulling his gearshift more... exciting.
He slid his hands over the cabin and straddled the front, grinding his panel into it with his back to the windshield, hands braced on the hood.
He popped his panel open and dipped several fingers into his cable sheath. He fondled the tip, coaxing it out, letting a quiet moan spill from his vocalizer.
As his cord extended, the 'Con ran his fingers along its length, enjoying the little shivers his own touch caused. His processor supplied him with the fantasy of blue servos instead of his own.
"Mmmm… You have gentle hands, Optimus." The red 'Con purred to himself, his cable pulsing in his grip. He palmed the head and quivered at the too-strong sensation. It was so nice being able to play with his bits without hurry, instead of just racing from zero to sixty.
He leaned back onto the windscreen and let his legs fall apart even more, brushing fingers over the panel which housed his valve before retracting it. Optics offlining, he imagined a hungry blue stare devouring him, then pushed one finger inside just so, lubricant dribbling out onto the hood of the truck...
"I'm so wet already," he purred and thrust the finger deeper, his body arching at the sudden stimulation.
"Mmmm, Optimus..." Lost in his fantasies he didn't notice a slight change in the trucks temperature.
Optimus rebooted slowly. Before all his routines came to life he was confused about his whereabouts.
First thing he registered was weight all over his hood and windscreen. He didn't panic; he often found cats and dogs curled and asleep on him – probably something about his internal heat. Only this thing on him was bigger. Much bigger, and it moved, and writhed... and oh...
He registered the wetness on his hood with curiosity.
His temperature spiked as he caught the telltale smell of lubricant.
His optic sensors booted up and he was greeted with a most delicious picture: The red 'Con sprawled out on top of him; the delectable mech writhed as he pulled on his cord, other hand buried deep in his valve, leaking all across his hood.
Moaning his name.
Optimus' internal temperature spiked drastically as tactile sensors in his armor activated. He could feel every movement, every grind of the red plating on himself, and he rumbled quietly in delight.
Oh, this was a most delicious, even if not anticipated, turn of events.
Knock Out leaned forward, presenting Optimus with a perfect view of his open valve. The Autobot's cord throbbed as he imagined sinking inside it, pushing the 'Con to the ground and simply taking him.
"Oh yes, Optimus, yes," Knock Out ground his cord on Optimus' hood and kissed the blue finish, trailing his glossa over the armor, whimpering.
"Mmm, you're such a strong mech." He reached one hand back and thrust fingers inside his valve.
Optimus choked back a moan at the cry that Knock Out muffled against his plating.
The 'Con was pleasurable to look at – perfect finish, smooth silky lines, cocky smile, and now he was giving a show that had Optimus wanting to transform and frag him senseless.
He sensitized his plating and let himself enjoy every brush, graze, and impact.
As his body heated up he couldn't stop his fans activating. He transformed, catching Knock Out as he fell down off his hood, and pinned him to the ground.
Knock Out's shocked gasp, as the realization of what had just happened hit him, made Optimus smile broadly.
"You were leaking all over me, Knock Out. You made me... dirty." The 'Con struggled under him feebly.
"Mmm, I can get you cleaned later; now if you don't mind, I was in the middle of something there."
"Aren't you a cheeky little piece of shareware?" Optimus purred.
"Aren't you a big, naughty Autobot?" The 'Con arched his hips off the ground, seeking friction.
"Be my guest then, and... continue what you've started," Optimus said in a low tone, dumping the heat through his front vents straight at Knock Out, the Decepticon Medic squirming deliciously under him.
"Wouldn't you rather... partake?" Knock Out cocked his head flirtatiously.
Optimus dropped his voice another octave in response. "Mmm, but you were making such an exquisite show of yourself. I wouldn't want to spoil it."
"You sure, gorgeous?" Knock Out arched up, his panel almost touching Optimus'.
The Autobot growled in response, his interface pinging him request to open.
Knock Out looked him in the optics and palmed his cord, the red lights flickering in pleasure, lip-plates parting in a quiet mewl.
"You like to show off, don't you?" Optimus moaned. "Have someone watch you rev your own engine?"
Knock Out only purred in response.
The Autobot dragged his optics along the red frame, taking in every curve, from the wide shoulders to slim hips and strong legs. He sat back against the wall and watched.
Knock Out propped himself on an elbow and spread his legs wantonly, presenting Optimus with a perfect view of his equipment. He stroked his cord, hips rocking into every movement.
"And you like to watch, don't you? See someone spread before you? I can see you eating me up with your optics."
"Who would refuse such a show?" Optimus clicked his panel open, cord extending into his hand. "Mmmm, who would miss an opportunity to watch such a shameless slut whoring himself for my pleasure?"
"Big on human swearing?" Knock Out smirked and threw his head back, last word morphing into moan as he thrust fingers inside his valve. "Fuck you, Prime."
Optimus growled, optics glued to fingers disappearing in the valve, three digits moving, stretching... showing off.
Knock Out leaned down, his vents circling fast as his second hand gripped the cord and stroked it frantically, quiet moans and grunts spilling from his vocalizer.
"Mmm, such a little... Oh yes..." Prime grunted and squeezed his own cord as he saw Knock Out's valve clenching over his fingers. "Mmm, I want to see you overload all over yourself," Oprtimus demanded, the 'Con moaning at the words.
"Frag, you are such a..." an indecipherable sound followed as his hand sped up on the hard cord, movements impatient, vocalizer resetting suddenly as Knock Out's hand stilled on the base, letting it twitch and shoot a load of silver fluid across his chassis, valve clamping over the fingers inside.
The 'Con relaxed his body and withdrew his fingers only to trail them through the transfluid on his chest.
The 'Con smirked and looked defiantly into Optimus' optics, before promptly gasping, seeing how the other's optics burned into him with a single, driving force:
With a feral growl Optimus was over Knock Out, pushing his legs wider, pressing him down with his weight, fighting the urge to just slam home into delicious, wet valve. Instead he positioned himself, wary of the size difference, and rocked slowly inside.
"Frag, you are heavy duty, nngh." Optimus thrust deeper into the still tight valve.
"Thought you liked big mechs…" Being halfway in he looked into the other's optics, and after withdrawing, thrust all the way in.
"Frag, yes!'" Knock Out bucked under him and Optimus pulled out slowly, the medic whimpering helplessly.
He pushed back quickly, making the 'Con cry out again. The tight heat of Knock Out's valve made his processor spark with pleasure, enveloping him and sucking him in with every thrust.
Optimus grabbed one silver leg and hiked it up, red hips riding higher - a perfect position to just pound into that luscious valve.
When he grabbed the red hips, fingers digging into red plating, Knock Out dug his fingers into his hands and keened, long and low.
"You like to be fragged like that, hmm?"
"Slag, shut up... Primus, Optimus..." Knock Out's optics lost focus as he hung on for dear life, Optimus riding him hard.
A few more thrusts had that sinful valve clamping around Optimus' cord, keeping him inside, pulling the climax from him.
Optimus overloaded with a grunt, transfluid spilling inside, Knock Out going slack in his arms.
He pulled out with a quiet moan, smirking at the thin dribble of mixed fluids running from Knock Out's valve.
He quickly wiped all the transfluid from his panel – no need for unnecessary stains – and tucked the cord back inside.
For a moment he had the completely mad desire to lie down and, of all things, cuddle the Decepticon.
Sending info to agent Fowler that their meeting place was compromised, he considered cleaning Knock Out's armor for a moment, but after a moment of deliberation he only smirked and subspaced his rag.
Knock Out was first and foremost a Decepticon, and he would not let an opportunity slide.
Knock Out came to Starscream glaring at him furiously.
"What in the pit do you think you are doing?"
"Commander Starscream, I was just..."
"And what is that?" Starscream pointed at his chest.
Knock Out looked down and let out undignified squawk of fury. Watching him from his chest, painted in dried transfluid, was an Autobot sign.
"Nevermind, I don't want to know, but I believe it should be enough punishment if I forbid anyone to buff it out for the next ten cycles."
Right then Knock Out promised himself to never let himself be fragged by an Autobot again.