Dream on. That’s what we say to reports that Aerosmith will be playing Imperial Cars’s summer auto show in Mendon next month. The rumor has been spreading on Twitter and Facebook, prompting the Mendon selectmen to put the issue on the agenda for Monday’s meeting. The show, set for Aug. 16, features food, free carnival rides, and, according to the dealership website, “plenty of great music.’’ Reasons we don’t think Steven Tyler, Joe Perry, Brad Whitford, Tom Hamilton, and Joey Kramer will be performing? First, the band is scheduled to play in Osaka, Japan, that night. Second, it’s a car show in Mendon. Organizers could not be reached for comment.