Brush mussels very well under cold running water; drain them well.
Heat 1 tablespoon vegetable oil in a saucepan. Add 2 teaspoons garlic and mussels and cook for 30 seconds. Add wine and 1/2 cup water; cover and cook for 2 minute or until the mussels are all open. (Discard the ones that stay closed.) Remove the mussels with a slotted spoon. Remove the top half of each shell, leaving the mussels intact on the bottom half of the shell. Arrange the mussels on a serving platter.
Heat a large heavy nonstick skillet over medium heat. Add remaining 3 tablespoons vegetable oil and remaining 1 teaspoon garlic and cook until the garlic becomes fragrant. Turn off heat. Stir in oyster sauce and cilantro, mixing well. Spoon over the cooked mussels and serve. Makes 4 servings.