Rust
After Dean's death, and after Sam has finally stopped crying, the first thing he does is tune up the Impala.
He's not very good at it; Sam knows that he'll never be as skillful as his brother when it comes to taking care of the Impala, but that does not mean that he's not going to try. Sam's stubborn, and he can remember a vast amount of times during their childhood where besting his big brother was all he could think about. If Dean could pick a lock in under three minutes, then Sam could do it in two, and if Dean could hit the target dead center, then Sam could do it as well.
Sibling rivalry. It was always about who was better than who. Sam scoffs at his thoughts. It's also gotten us into trouble more times than I can count.
But the car was, is, Dean's and Sam knows that he'll never be able to best his brother at this, at something that he'd been doing practically his whole life. There are four things that Dean knows better than Sam, and Sam will wholeheartedly admit it to anyone who asks. Women. Hunting. Taking care of the car. And taking care of his little brother.
Sam smiles, but tears well up in his eyes and he wipes them away with the sleeve of his hoodie. Damn... he's been gone for a week and Sam still can't even look at the car without thinking of Dean. The taller man gives a choked laugh as he leans over the hood of the Impala, watches as the small tears hit the metal with soft plunks.
Sam doesn't stay like that for long, he's got a job to do after all and with a heavy, ragged sigh, he straightens up and sets to work; utilizing all the important lessons Dean's taught him over their last year.
That's my job, right? Showing my little brother the ropes?
The work is hard, mostly because Sam's hands are shaking so bad he has trouble getting a good grip on the tools; he stifles a curse as the wrench once again slips out of his fingers and clatters to the ground. More than anything, though, he's afraid of messing up, scared he'll screw up the car so bad it won't even start; because Lord knows he has barely any idea as to what he's doing.
But he tries.
He takes care of the Impala, takes care of her – because Dean would have kicked his ass for referring to the car as an it – just like his big brother had shown him how to do. He's diligent, focused, doesn't stop till her surface is gleaming and he can see himself - red-rimmed eyes and all – staring back at him through the paint.
And everyday for two weeks it's the same routine: wake up, eat, shower if he has to, get dressed, drive to the next piece-of-crap motel, and then take an hour to clean the Impala before heading out to hunt down whatever evil son-of-a-bitch is out there. Rinse. Lather. Repeat.
Sam cleans the car after hunts too because he sure as hell isn't going in and out of battle with the Impala looking like one of the cars Bobby has sitting in his yard. Dean would certainly kick his ass if he knew that his little brother was letting his car rot like one of Bobby's pieces of junk.
Sometimes, though, working on the car is just too much and Sam has to stop for a while to catch his breath. Sometimes he cries. Sitting on the hood, it's just him and the car, alone, on the highway with whatever tape he's picked from Dean's massive collection blaring through the speakers. He sleeps in the car too; his long body curled up in the back seat just like he had done when they were little with no motel to go to and staying at Bobby's or Pastor Jim's wasn't an option. It's uncomfortable, sure, but Sam doesn't mind. The Impala is their home and the only thing, besides the golden amulet that Sam now wears proudly around his neck, that Dean cared about more than anything.
Well, besides Sam of course. Dean would throw away both the car and the necklace without a second thought if it meant saving his little brother's life.
So Sam takes care of them, takes care of the car, as if she were his own. Keeps her clean and neat , washes the windows, waxes her, vacuums the floor, and tunes her up when necessary.
He supposes he should find it strange when, after Ruby comes and finds him and fills his head with thoughts of training to kill Lilith, and after being ignored for weeks at a time, the car doesn't show any signs of age or rust.