The neutralization reaction between a concentrated sulfuric acid droplet and a series of model marine cylinder lubricants (MCLs) formulated with an overbased sulfonate and a series of different nonionic surfactants was studied using a capillary video-microscope technique at room temperature and a phase transfer neutralization rate test at several temperatures up to 55 degrees C. The model MCLs were characterized using dynamic light scattering and transmission electron microscopy. On the basis of the observations, a mechanism is proposed fur the neutralization reaction which involves the initial formation of a mixed reverse micelle system between the overbased sulfonate and the nonionic surfactant followed by the neutralization reaction at the aqueous acid/oil interface to form calcium sulfate crystals. The rate of the neutralization reaction is enhanced by the presence of the nonionic surfactants in the model MCLs and is consistent with the formation of the mixed micelle systems which makes the basic core (CaCO3/Ca(OH)(2)) of the overbased sulfonate more accessible to the aqueous acid due to the increased size and flexibility of the overbased sulfonate reverse micelle.