In a small bowl, mix 1/3 c soy sauce, 1/3 c brown sugar, 1/3 c water, 1/4 c vegetable oil until sugar dissolves. Pour into large ziplock with fish, seal, and turn to coat. Refrigerate 2+ hours.

Discard marinade. Preheat grill, lightly oil, then cook salmon 6-8 minutes/side, until it flakes with fork.