The solubility behavior of three renewable bio-liquids obtained from hydrothermal liquefaction, rapeseed oil, and two common refinery streams is investigated. 242 solubility tests are performed, which lay the foundation for testing three different solubility approaches, namely: Hildebrand, Wiehe, and Hansen solubility parameters, and gaining a better understanding of the blending capabilities of bio-liquids into refinery streams. Finally, a theoretical investigation of common bio-liquid model compounds is undertaken. Results show that the Hildebrand solubility parameter is inadequate in predicting the solubility behavior of bio-liquids and should not be pursued in trying to derive a method for predicting compatible matches of complex liquids. The two-dimensional Wiehe solubility parameters are accurate in predicting pure solvents and nonsolvents for such complex liquids. However, the Wiehe approach is incapable of predicting the mutual compatibillity of bio-liquids, too. The Hansen solubility parameters show a compatibility wall defined by a distance calculated in the Hansen space. Although an overlapping region exists, it is expected that further experiments can help defining a threshold value below which compatible matches can be found. A conservative estimate is that any binary mixture of complex liquids chemically comparable to those under investigation, having a mutual distance below 4.9 in the Hansen space, are compatible.