United Hydro Vesta Hydraulic Oil HT- 4 is the Transmission & Drive Train oil (TDTO) for the Caterpillar TO-4 oil specifications that may not only include the frictional requirements, but also gear wear requirements. Besides meeting Caterpillar TO-4 oil specification, it offer maximum protection against mechanical wear; rusting and corrosive wear in all hydraulic and hydrostatic transmission systems.