Analysis of Co effect, introduced instead of Mn into a high-temperature weldable 1151 alloy at presence of small additions of transition metals of IV (Ti, V) and V (Zr) period on the alloy fluidity is given. The effect of each separate metal and a combination of two and three used transition metals is shown. The effect of Mn and Co on the alloy fluidity under conditions of complex alloying is compared. The work was carried out using the experiment planning method (linear factor plan). The results are presented in the form of tables and diagrams.