If the oil is stored right-side-up the additives can settle to the bottom of the bottle and stick there when you pour the oil into the engine. If you store the bottle upside-down the additives will re-mix with the oil as you pour the bottle into the engine since if the additives do stick it will be in the cap area on the neck where all the oil goes past before sliding its slick self into your crankcase
This is also why before you put oil into your car its a good idea to give the bottle a good shaking like it were a can of paint.
Threaded Mode