Bill Ross IV and Turner Ross’s Gasoline Rainbow is an unusually poetic road film, as it has less in common with cut-and-paste teen party flicks than it does with the existentially freighted sensibilities of The Endless Summer, Two-Lane Blacktop, and even The Outwaters. Blending documentary and fictional elements together as they have in films like Western and Bloody Nose, Empty Pockets, the Ross brothers fashion an aesthetic that’s something like the best of both worlds. Gasoline Rainbow’s teenagers are rendered with unusual realism, while the imagery has the resonance and intensity that speaks of the resources and planning that’s typically associated with fictional films. It feels simultaneously “of the moment” and retrospective—a subtle yet formally extravagant teenage daydream.

For viewers who’re removed from their high school years, the realism of Gasoline Rainbow may require acclimation. The film’s teens—Tony (Tony Abuerto), Micah (Micah Bunch...