But in Your Dreams (Whatever They Be)
Five times people passed out on Dean, and one time he returned the favor.
+1.
Sam's loud, "WHAT THE FUCK ARE YOU DOING, DEAN," delivered directly into his right ear at 200 decibels, jerks him out of his doze and into the present, which is driving down the highway at two am and seventy miles an hour, about two seconds from plowing into an eighteen-wheeler's back end.
"WHOA SHIT," is his response, and he wrenches the wheel to the side. They miss hitting the semi by inches but shoot straight into oncoming traffic, and Sam's constant stream of "Ohshitohshitohshit" lasts until Dean dodges the last minivan and veers smoothly back into the right lane, hands white-knuckled and heart pounding.
Sam' harshly panted, "Pull over, Dean, I swear to God I will kill you if you kill us," is nonsensical but sincerely threatening and Dean obeys, slowing and easing off the asphalt onto the gravel shoulder. They come to a complete stop just as the semi passes them, laying on it's horn with justifiable gusto.
Dean's still fumbling with his seatbelt when Sam wrenches the driver's-side door open, glowering down at him in all his towering Gigantor rage. "Why didn't you say you were getting tired? No, forget it, just get out."
The back door opens and Castiel pokes his head up above the window, hair sticking up in every direction and a reverse pattern of the Impala's leather seat creasing his cheek. "Are we there yet?" he asks, eyes unfairly bright and clear for the time of night.
"We're rotating drivers," Sam answers, shoving Dean out of the way. "Cas, switch spots with me and let Dean have the back?"
The adrenaline from nearly ramming the big rig is fading quickly and Dean's falling asleep where he stands. His eyes blink open as one of their old scratchy army blankets settles around his shoulders, and he mumbles a thank you and stumbles forward towards the back. Castiel's hand on his head is the only reason Dean doesn't bash it on the Impala's frame as he crawls inside.
It's warm and dark, and Dean sighs blissfully as he draws his legs up to his chest and puts an arm under his head, already drifting off again. The car rocks as the doors close—one, two, three—and the driver's seat slides back as Sammy Long-Legs gets comfortable. Probably fucking up his mirrors, too. Bitch.
"Okay, you remember I told you the Impala has a manual transmission?" he dimly hears Sam say to Cas, who murmurs agreement. "Right. You use the stick shift and the clutch pedal to switch from gear to gear—"
The engine purrs to life, and Sam's voice blends with the low roar of the Impala's engine and, as they pull back onto the highway, the road moving under her wheels. It's been Dean's lullaby for most of his life, and he falls asleep with the feeling that—for once, for just this moment, these few hundred miles in the quiet dark—everything is as it should be.
One kind reviewer pointed out that not only does the Impala not have seatbelts, it also has an automatic transmission. Please, continue to suspend disbelief despite these oversights. :)