I bought a used 2008 Prius a couple weeks ago. The car was running fine until a day or two ago. I would normally get 40 MPG. Now I am getting 30. While driving I am also noticing that the engine is very loud - it was not like this before. I connected an ODB-II tool and noticed the engine is revving to 5000 RPM. The car also feels like its not "shifting" (although I know it doesn't have gears like a normal transmission) until I let my foot off the gas. Also, the battery is dropping to 2 bars (purple) which I did not notice happening before, and the engine becomes even louder. The ODB-II does not find any fault codes and there are no warning lights on the dash either. I washed the engine compartment with a high-pressure hose. The engine was off but the battery was not disconnected. I don't know if this could be the cause of the problem (not sure if it started before or after this) Thank you for any help.