Just changed out my 07's factory 12v battery and replaced it with a optima battery from elearnaid. I notice my MPGs dropped by 10pmg. Current weather in North NJ: 85degrees, partly sunny, AC on at 77 LOW. Since I purchased this used car about a week ago, I was averaging 42MPG in 90+ degree weather. I would think after changing to a new battery I would see MPG improvement. I'm currently getting 28MPG! Should I panic?
no. did you charge the battery before installing? did you reset mpg meter for a fresh read? how far have you driven on new bat?
I didn't charge the new battery - didnt know I was supposed to since it's new. I did reset the mpg on the mfd. I've been driving 20 miles so far and it just went to 34mpg.
Sounds like it is charging up. A slow charge to top it off would be a good idea. New doesn't always equal fully charged. The other assumption is that the old battery needed replacing because of low voltage. So far it sounds like it was better than the new one.
As SteveLee said, the battery was probably shipped without a full charge. Reputable dealers usually have a stash of batteries topped off before the ship. It may also be a bad battery. Just keep an eye on it for a few days and see how it goes before you jump to any conclusions....
Also, changing the 12v battery would clear the computers. The car is still learning the way you drive and, from what I've read, the MFD takes a while to calibrate, too.
Optimas are usually pretty good, though overpriced like all direct replacements. There have been some reports of Optimas received with low voltages. Check with voltmeter. Or you can check with the on-board system method found here. Weird stuff happening? MPGs dropping? Test The Battery | PriusChat You can use just the parking lights to save on stressing the headlights. Report all three values back here.
Must have been like either the battery is now charged or the computers have caught up or both. Glad it ended well. Enjoy!
This was my first thought. I've seen reduced mileage for as many as two tankfuls after a complete power down.
