Systems and methods are provided for co-processing of biomass oil with mineral coker feeds in a coking environment. The coking can correspond to any convenient type of coking, such as delayed coking or fluidized coking. The biomass oil can correspond to biomass oil with a molar ratio of oxygen to carbon of 0.24 or less on a dry basis. Such types of biomass oil can be formed from pyrolysis methods such as hydrothermal pyrolysis, and are in contrast to biomass oils formed from pyrolysis methods such as fast pyrolysis. By using a biomass oil with a molar ratio of oxygen to carbon of 0.24 or less, improved yields of light coker gas oil can be achieved in conjunction with a reduction in the yield of heavy coker gas oil.