A semi-industrial bioscrubber was developed to treat a complex mixture of VOCs: oxygenated, aromatic and chlorinated compounds. In order to optimize the VOCs mass transfer, an original washing agent made up of water and cutting oil was tested, and the impact of this washing agent on bioscrubbing performances was investigated. The results obtained with a laboratory unit show that the addition of oil strongly increases the quantity of transferred aromatics. For these compounds, the apparent mass transfer coefficient k(L)a is lower than with water alone. In term of bioscrubbing performances, comparison of the results obtained with the water-oil mixture and water alone showed that the removal efficiency for aromatics is enhanced: from 12% to 36% (applied load of 852 g VOCs m(-3)h(-1)); the elimination of chlorinated compounds is slightly improved. The addition of oil does not seem to lead to any dysfunction of the microbial communities that metabolize the transferred compounds.