Mix oil, flour and salt together in a medium bowl. Add a drop or two of red food coloring to give your volcano a more authentic aesthetic. Beginning with 1/2 cup of water, fully incorporate the ingredients into a thick yet workable dough.
Cover all but the top of your bottle with your fresh dough, molding it into the shape of a mountain. Give your volcano character by shaping craters and mounds across the entire exterior.
Set your volcano model in the middle of a cake pan or metal tin. If you desire, squeeze a few small streams of red food coloring around the very top of the volcano's mouth, letting them dribble down the mountain for a striking visual lava effect. Allow the dough to dry onto the bottle overnight.
Fill your bottle with hot water to within a few inches of the brim. Squeeze four or five squirts of liquid detergent into the bottle. Add the baking soda. Put one or two drops of red food coloring into the bottle, if desired.
At the moment you are ready for your volcanic eruption demonstration, fill the rest of the bottle with vinegar. After the initial eruption, pour in more vinegar if you want the volcano to erupt again.
Let the eruption settle for at least 5 minutes before cleaning the pan. Gently pour out the contents of your bottle, making sure to keep your dough intact. Rinse the bottle with water and wipe down the exterior of the volcano model with paper towels.