The influence of synthetic surfactants and vegetable oils and their derivatives on the stability of Ashal'cha (Tatarstan) crude oil asphaltenes against precipitation is studied by methods of titration with n-heptane and determination of the quantity of the precipitate separated by reducing the dissolving power of the dispersion fluid. It is found that bioadditives containing -COOH and -OH groups in the molecule enhance crude oil stability most effectively. It is proved that loss of crude oil stability occurs upon injection of certain additives containing several polar groups in the molecule, which facilitates formation of bonds between asphaltene aggregates. In experiments simulating compounding of heavy and light paraffinous crude oils it is shown that addition of surfactants to crude oil blends, rather than to heavy crude, is most effective.