Oil-type transformers (OTT) are used more than dry-type transformers, based on cost in the transmission and distribution of electrical energy. Therefore, this usage density increases the importance of cost in OTT. Weight is important in transformer cost. The weight of the transformers depends on the variable parameters of the weights of the core and windings, C (iron cross section conformity factor) and s (current density), respectively. In this study, unlike the previous heuristic optimization studies, an innovative and complementary optimum weight was obtained by using the Gray Wolf - Whale Optimization hybrid algorithm for both distribution type and power transformer type OTT. A weight reduction of 44% and approximately 14% in power transformers was achieved. It was determined that this decrease in weights provided the same reduction in OTT costs. The comparison test of the study was performed both with the values of other algorithms and statistically.