dear scotty i have prius S 2013 model and i have chaned its transmission oil and coolent but after that change my car's milage has dropped by 100 km.need your suggestions.....ATF WS was used as tx oil and branded toyota coolent was used

see that ALL the time. i would ONLY use toyota tranny fluid in that vehicle, it's very special fluid. Any change can create more friction and lower gas mileage