You have a relatively small sump size on this motor. I would think that a single bottle application would be adequate. Usually the double bottle fast track is used for car motors with heavy sludge or for vehicles that are driven very sparingly. In your case use a single bottle in combination with an oil change interval of conventional oil. Also in the Prius you may want to drive a bit more aggressively or perhaps some highway runs whereby the gasoline motor is doing more of the powering than the electric side of the power generation.
