We study surfactants at the oil/water interface using Dissipative Particle Dynamics simulations at constant μsurfPT. The interfacial tension depends on the surfactant branching in a subtle way. For a given interfacial concentration, a double-tail surfactant is more efficient than its single-tail isomer only if the oil-head repulsion is sufficiently strong. For a given concentration in the bulk water phase, the single-tail surfactants are more efficient in both cases. We interpret these results in light of the molecular packing at the interface and free-energy considerations.