In an embodiment of the disclosure, mixtures of different carbon length alcohols are used as the primary feedstock for Guerbet alcohols. Specifically, embodiments relate to a method of synthesizing mixed molecular weight additives from a mixture of primary alcohols comprising, receiving a mixture of primary alcohols having greater than two different chain length primary alcohols and reacting the mixture of primary alcohols in a single reactor to produce a mixture of at least five Guerbet alcohols. The mixture of Guerbet alcohols can then be used to produce an additive or surfactant composition comprising additives or surfactants of different molecular weights.