Chuck Vincent is one of those rare directors of X-rated and exploitation films that even his detractors will begrudgingly admit had the ability to make a great movie. He was an actor's director, for sure, giving meaty and complex roles to his stars. Although best known for his pre-code esque comedies and character driven melodramas, in the first few years of his career, Chuck tried his hand at a whole slew of genres, including this odd and effective road movie from 1973.
Gene (Bo White) and Tracy (Darcy Hollingsworth) are two high school friends who decide to take a last roadtrip together in their absurdly decorated van, which they've named 'The Meat Wagon.' Ostensibly, the purpose of their trip is to bed as many young women as they can and they quickly pick up a couple of teenage runaways who nearly rob them blind. Next, they end up at a small town diner where a local invites them to join him on a date with the town nymph, but only if they pay for the beer. But before Gene and Tracy can get in on the action, they're chased out of town by the woman's violent husband. And so their adventures go, periodically interrupted by the ominous presence of a Hell's Angel looking biker who may or may not be stalking them.
Blue Summer presents itself and was marketed as a softcore fluff piece; merely another mindless sexploitation flick for the middle section of a drive-in triple bill. But beneath it's rather superfluous surface lies one of Vincent's most agonizing and subtext laden dramas. At its core, Blue Summer is a story of homosociality, but more specifically, homoeroticism. From the first scene through the last, the strongest sexual tension lies between Gene and Tracy, mostly in the form of Gene sexualizing Tracy, though the film's final shot would seem to imply that their unspoken desires were mutual.
An early pivotal scene occurs as the two have settled down with their teenage hitchhiker pickups. As Tracy starts having sex with his girl in a tent, Vincent cuts to Gene, seated with his 'date' next to a fire, completely ignoring her and notably fixated on the tent. When she jokingly asks why he hasn't made a move yet, and if he's a virgin, Genre defensively answers "No! Why would you say that to me?" then proceeds to aggressively fuck her next to the fire, so as to reclaim his challenged masculinity. 
Subsequent parallels, such as after Gene and Tracy have had a foursome in a field with two hippie chicks, as their male leader watches and plays the flute, show the hippie girls asleep that night in the arms of their man, while Gene and Tracy sleep together, fully nude, in their tent. Ultimately, Vincent's thesis appears to be that the two friends are using their rabid sexual appetites as a bizarre form of posturing to disguise their lust for each other.
But more than just a harsh examination of homoerotic repression, Blue Summer adeptly explores sexuality as something frequently tinged with regret. No sequence in the film better presents than than Tracy's final tryst, with a lonely older woman whose teenage son, clearly the same age as Tracy, comes home shortly after their lovemaking. The obvious shame felt by her, as her son, oblivious to his mother's actions, is nearly heartbreaking. 
And such is the tone as the film ends, obliging the viewer to contemplate what could have been, but offering no solution other than reflection on missed opportunities that can never be fulfilled.