The increasing global adoption of electric vehicles (EVs) has shifted the focus of tire research toward enhancing fuel efficiency and abrasion resistance. In this study, we propose triethoxysilyl-terminated telechelic liquid butadiene rubber with disulfide linkages (Si69-LBR) as a processing aid in the tire tread compound to enhance tire performance. The triethoxysilyl groups at both ends of Si69-LBR form covalent bonds with silanol groups on the silica surface, and the disulfide linkages in Si69-LBR additionally cross-link with the base rubber. Si69-LBR was synthesized via a "one-step" process using Si69, containing bis[3-(triethoxysilyl)propyl]tetrasulfide, as an iniferter (initiator-transfer agent-terminator). Compared to the compound applied with 40 phr processing oil, the compound in which 10 phr was replaced with Si69-LBR exhibited enhanced migration resistance, abrasion resistance, and fuel efficiency of 21, 20, and 7%, respectively. These results explain the effect of the functionalization of LBR and the additional cross-linking resulting from sulfide bonds in Si69-LBR.