Next to a red MX-5 in the glow of Mazda's stand at the New York auto show, Geraldina Posada, 18, and Sky Quiceno, 19, discuss the benefits of posting on Snapchat, the social-media site favored by the likes of DJ Khaled, or Facebook Inc.'s Instagram. "When you see a good car, and you like it, you put some filters on it and then -- boom, you have a picture that can get hundreds of likes" on Instagram, said Posada, who uses one account for her artistic photos and another for her social life.