New version of thermodynamic aggregation model of asphaltene-containing crude is formulated and analyzed with regard to characteristics of resin molecule shape and deformation of the resin shell of the asphaltene aggregates. The relation between the shape factors and elastic constants is discussed, and their effect on the size distribution of asphaltenic aggregates is considered. The model is applied to describe asphaltene precipitation from petroleum fluid upon its dilution with a liquid alkane. The effect of dilution on the asphaltene particle size distribution is studied. The model calculation has shown that the behavior of asphaltenic crude varies dramatically with the change of molecular characteristics of resins.