I've had my car for a little over 2 years and usually average 48-56 mpg, and lately it has been struggling to get up to 30 mpg. I've been consistent with oil changes, tire rotations, keeping the correct PSI in my tires, making sure fluids are good, etc. I've also had no change in trips, driving patterns, A/C usage, or anything. Literally everything has been held pretty constant, just a sudden drop in my mileage. Could it be the 12 V battery? I've put 52000 miles on it since I've had it from only 10 miles, but just don't see why it would suddenly drop?
Sometimes bad gas can do this, or not correctly having the amount of gas in the tank you thought you had. Once this is beyond just one tank of gas, it's time to start doing some diagnosis.
Look through this list for ideas that you might have missed. (Not being a new Prius owner, not everything in here applies to your case, and I don't think you need to post the answers for us) -- Fuel economy complaints/queries? Please copy, paste & answer these questions, esp. if you're new | PriusChat The biggest thing missing from that list is brake pad drag. This can be checked by feeling the hub temperatures after driving, to make sure they are not getting too hot.
welcome! certainly worth testing the 12v to begin with. have you ever discharged it? how are you measuring mpg's, calculated when refilling?
