Preheat the oven to 350°F with a rack in the center position.
Grease an 8 x 8-inch baking dish or line with parchment paper.
In a large bowl, combine the oil, water, granulated sugar, brown sugar and vanilla. Stir in the eggs, until the batter is glossy. Stir in the flour, cocoa powder and salt, until just combined.
Pour the batter into the prepared baking dish and bake until a toothpick inserted into the center of the brownies comes out clean, about 28 minutes. Let brownies cool for at least 10 minutes before cutting into 9 pieces.