Chicago Reader review:
Not quite a disco musical, this sure feels like one in terms of bounce, verve, and energy. It's basically a comedy-drama built around a string of vignettes related to a day in the life of a Los Angeles car wash, with a very good, largely nonwhite cast featuring Franklyn Ajaye (a particular delight), Antonio Fargas, Bill Duke, Ivan Dixon, Richard Pryor, Tracy Reed, and Garrett Morris; Sully Boyar plays the white boss. The gags tend to be much more concerned with questions of class than one is accustomed to in American movies—and the contrapuntal punctuations of the disco DJ are positively Altman-esque. Michael Schultz (Cooley High) directed a screenplay by Joel Schumacher, and if you compare this movie to Schumacher's somewhat similar D.C. Cab, made seven years later, you may conclude that Schumacher's is the dominant creative voice. Critics seemed to like this less than audiences; personally I had a ball (1976).
Here (and above) is the trailer.