Abstract: A fuel and oil mixing device holds a quantity of fuel and oil and allows a user to easily select the ratio of fuel to oil in the mixture that exits the device, thus allowing a single device to be used to fill multiple two-stroke engines. The fuel and oil mixing device includes a mixing chamber defining an internal volume, a fuel intake opening, an oil intake opening, and an outlet. Fuel is delivered into the mixing chamber from the fuel reservoir through the fuel intake opening, while oil is delivered into the mixing chamber through the oil intake opening. An oil control valve controls oil flowing into the mixing chamber through the oil intake opening so as to allow the user to dispense a fuel-oil mixture through the outlet of the mixing chamber with a predetermined fuel-to-oil ratio.