Taco Bueno publishes a real per item ingredient list, and it shows soybean oil in 123 of their 125 menu items, with only the Black Beans and Cilantro Lime Rice free of it. Artificial additives are widespread too, including potassium sorbate in 73 items, MSG in 65 and TBHQ in 41, though the guacamole is genuinely clean at just avocado, tomato, onion, salt and jalapeno.
Taco Bueno is one of the very few chains that actually publishes a per item ingredient list, and it does them no favours. Across the 125 menu items in their own ingredient PDF, soybean oil appears in 123. The only two without it are the Black Beans and the Cilantro Lime Rice. Palm oil is in 78 and beef fat in 54, and 35 items list an unspecified vegetable oil defined as one or more of soybean, corn or cottonseed. Their own disclaimer says soybean oil is used in some of their products, which undersells it badly. The additives are the same story: potassium sorbate in 73 items, MSG in 65, caramel color in 62, TBHQ in 41, BHT in 17, and Yellow 5 and Yellow 6 in 22 each. The BHT is all in the steak marinade and the dyes are all in the queso, so avoiding steak and queso avoids both. The one bright spot, and the only item I would call clean, is the guacamole: 100 percent hass avocados, tomatoes, onion, sea salt and jalapeno. Their document is undated and its filename says 2016.