Hydraulic control system for engine

A hydraulic control system for an engine having a plurality of cylinders, comprising:

• a valve stop mechanism comprising a spring, the valve stop mechanism switches the engine from all-cylinder operation to cylinder cut-off operation in which the spring is compressed relative to the all-cylinder operation, when pressurized oil is supplied to the valve stop mechanism, the all-cylinder operation being an operation in which all of the cylinders are operated, and the cylinder cut-off operation being an operation in which a part of the cylinders is stopped;
• a variable valve timing mechanism having an advance chamber and a retard chamber, which are defined by a housing that rotates according to rotation of a crankshaft and a vane body that rotates with the camshaft and which change a phase angle of the camshaft with respect to the crankshaft when the pressurized oil is supplied to the advance chamber and the retard chamber, the variable valve timing mechanism being capable of changing a timing to open and close valves mounted in the cylinders during the all-cylinder operation and the cylinder cut-off operation;
• an oil pump that supplies the oil to hydraulically operated devices including the variable valve timing mechanism and the valve stop mechanism through a hydraulic path;
• and
• a control device that controls operation of the hydraulically operated devices and the oil pump, wherein
• the control device controls a maintaining oil pressure, which is required to maintain an operated state of the valve stop mechanism during the cylinder cut-off operation, so that the maintaining oil pressure is set to a high value in a high oil viscosity region.