1967–2001[]
Diamond Shamrock started in 1967 when Shamrock Oil and Diamond Alkali merged.
2001–present[]
When Valero bought Diamond Shamrock in 2001, Diamond Shamrock changed its logo for the red bar to be on the top and the green diamonds on the bottom. Most Diamond Shamrock stations were turned into the Valero brand in 2005. As of July 2013 some of the Diamond Shamrock stations still survive, while Valero brought Shamrock Oil back after a 33 Year absence.