Hydraulic actuated valve gate systems make up less than 20 percent of the market. While they have a lower market presence in comparison to pneumatic systems,

they still fulfill particular industry needs, specifically in automotive molding.
Hydraulic actuated valve gates are especially common in automotive or large part molding. Because large tools often require hydraulic mold actuation, hydraulic power packs are required to run these molds. This makes it easy for the molder to hook up the hot runner system to the same hydraulic setup. Since oil is not as compressible as air, hydraulic systems tend to react slightly faster to the open and close signal. Hydraulic systems typically run around 1000 psi, which translates into a higher valve stem actuation force.

The downside is that if a leak occurs, either due to setup errors or wear of seals, the cleanup is considerably more labor intensive because of possible contamination to the machine, parts and the factory floor. Hydraulic systems also require more frequent maintenance to ensure proper operation. While the lower pressure of pneumatic systems is somewhat forgiving, in the case of a gate contamination (e.g., metal chips) or a nozzle shutdown, hydraulic actuation may induce damage to valve stems and gates because of the higher force exerted on the gate area.