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 comprising at least two different chain length primary alcohols and reacting the mixture of primary alcohols to produce a mixture of Guerbet alcohols. The mixture of Guerbet alcohols is then used to produce an additive composition comprising additives of different molecular weights.