Made by Streett in Maryland Heights, MO. A private label blender, making several different oils for others. Explore them for yourself at http://www.jdstreett.com/ .. I drive by this place several times a week. No possible way there is blending on site, just a small business office, and some warehouse storage.
Ah, memories of Strett's Zephyr stations when I moved to St. Louis in the seventies. STP used to be the Walmart house brand before Tech 2000 which was before Super Tech.
When I was in Oruro, Bolivia (quite a few years back) I used to buy STP motor oil. I used it for several years. I don't know how good it was but seemed OK. It certainly was better than what YPFB supplied. John--Las Vegas.