If people took the time to really see, the crinkles around Dean's eyes would tell them the whole story. It's the story of a boy who always stood in front of his little brother, a boy who stared out at the world, just a cold, empty dust bowl marked off by crossroads and populated by monsters, a boy who let the sun beat down on him while he stood still and gave cool shade to his little brother. They'd see a man who still walks in front, hoping to draw fire away from his little brother, alive only by his grace. A man whose eyes crinkle when he faces his little brother, as if looking at him is like gazing at the sun.
Dean sees himself as serving a grand and glorious purpose. Sam thinks he does it beautifully, just as the Impala does. And when Dean is washing his baby, stroking her with strong, reverent hands, washing away the gathered dust and coaxing her back to a high shine, Sam wants to do the same to Dean. He imagines his fingertips, gently wet, easing the fine grit out of the crinkles around Dean's eyes, and writing a new story.