Abstract: This invention relates to a proportional measuring device for determining the amount of oil that should be added to any quantity of gasoline that is added to the fuel tank of a two cycle engine to maintain the proper proportions of oil to gasoline for efficient operation of the engine. In the operation of internal combustion engines of the two-cycle type it is customary to add oil to the gasoline in the approximate proportions of one pint of oil per six gallons of gasoline to insure proper lubrication of the movable engine parts. Difficulties have heretofore been encountered in determining the amount of oil to add when a quantity of gasoline is added to a partially filled tank having the correct proportions of oil to gasoline. With my "Exact-Oil" measuring device it is possible to add any desired quantity of gasoline to a partially filled tank and then to determine accurately the amount of oil that should be added to that quantity of gasoline to maintain the proper proportions of oil to gasoline in the tank.