I bought a 2011 Prius with 113K miles on it 3 hours ago. Over the last week I test drove it twice, had it checked out by an independent mechanic, checked the carfax...everything seemed fine. The drive home was a less-than-20-mile mixture of stop and go traffic, highway driving, and idling in a parking lot. By the time I got home, the battery showed 7 lines of charge. I was home about an hour, then drove around the corner to my parents' (<1/8 mile). The car sat for about 10 minutes (shut off), then I drove back home. By the time I parked it, the battery had dropped to 2 lines. Is that kind of fluctuation normal? I'm not gonna lie...I'm scared to death the battery is going to end up junk and need to be replaced immediately.
If you haven't bought a plug-in Prius, you've got a battery that wasn't ever even meant to hold more juice than needed to average out the demands on the gas engine while driving. So it will be up and down a lot in normal operation. Any judgment you make in the first three hours of driving will be too much influenced by every detail of those trips to tell you much. I'd be inclined to just enjoy the car, as long as it is driving as it should and not giving you any warnings. -Chap
Here's a tip: Fill your tank and set Trip A to measure the mpg for the entire tank. Use Trip B to measure your shorter trips. The mpg you get on a full tank will help identify if your battery is in good shape. The Trip B for daily trips for let you know how your speed and driving techniques impact your fuel economy.
I filled up this morning. After about 25 miles, the average is 53.6mpg. I'll keep my eye on things; hopefully it'll stay right around there.
Not bad. Be aware that the car's computer is optimistic by 5-10%. You'll be more accurate by computing gallons at the pump versus odometer readings. But the car's computer is consistent enough to show trends.