The volume of a cylinder can be determined using the formula V = πr^2h, where r is the radius of the base and h is the height.
In this case, the width of the gas tank is the diameter of the base, so the radius is half of the width: r = 6 feet / 2 = 3 feet.
By substituting the values into the formula, we find V = 3.14 * (3 feet)^2 * 8 feet = 3.14 * 9 feet^2 * 8 feet = 226.08 cubic feet.
Therefore, the volume of the gas tank is 226.08 cubic feet.