10 mpg loss --->SOLVED!

Gen II (an '04) with 80K. It's been maintained per spec.

I suppose I need to check the oil. (Just learned about that.) I DID find one tire under inflated on the first leg of my drive which I inflated to 40 (the others were inflated to 40.) But mileage was better before I added air to the tire. Can't be sure about the winter formulation gas, but I don't see why we wouldn't have it...

Over night the battery will read 11.4 (one push of the power button, no brake). The IC does shut down at stops.

 

That does seem like a low voltage. If you EVER get the exclamation point on start up (with the car failing to go into ready), replace that battery immediately if you don't want to get stuck soon...You might also want to have the alignment checked if you haven't before; if the car is out of alignment there is more resistance and it definitely can cut mileage. I need to do this also, but I have to replace a rim before I do and so have been putting it off.

 

Agreed, the battery is near death. Along with the risk of getting stuck somewhere that can reduce MPGs, because the engine will run more trying to charge a battery that won't hold a charge.

 

Richard, this is getting to be a specialty of yours. Having Richard show up in a battery thread is like having a policeman and clergyman show up at your front door.

Tom

 

A bad sign?

Checked the voltage again this morning and it was 11.9V after sitting overnight (no load). Alignment doesn't seem to be an issue (it tracks perfectly straight).

[Was your avatar picture taken while climbing at the Red?]

 

Yes. I was climbing at the Red.

11.9V is low for a fully charged battery. Under no load, a fully charged lead-acid battery should read around 12.9V. Even powered down, the Prius puts some load on the battery, so 11.9 isn't as bad as it sounds, but it's not good either.

Tom

 

That route looked familiar, as did the Rhodies...

It is frustrating to think that a battery that is slightly degraded can have such a negative impact on performance. Even more so, because Toyota says that the battery is fine down to 9.5V...

 

I can't say enough good about the quick disconnect I installed for my Battery Manager (from Griot's, pretty much same thing as VDC's BatteryMinder). I've used it often and I could swear it's helped my SOC stay higher (subjective, placebo effect likely here!).

 

My brand new Toyota battery is ~12.4 tops with no load based on the MFD; was wondering (considering my commute is short each day) if I should have charged it after installing it Saturday; Toyota assured me it was unnecessary, but they are very often wrong about things. Should I? Should I be concerned about the voltage?

 

Ehh, it's probably fine. If you're worried and don't have an intelligent charger to put on it, you might leave the car ON in your garage or take it joyriding for a couple hours this weekend; then it'll charge itself.

 

I have a 2009 Camry and i wondering if my problem is the battery you discribe. I noticed after last winter the milage never recovered. Where i used to get 42 round trip without trying, not i have to try hard to get it. I was thinking perhaps the temp sensor was off and keeping the engin running longer, but this makes more sense. The symtoms I notice besides the drop in milage are: much more sensitive to turn the engine on from driving electric and takes longer to shut off engine when stopped.

I need an oil change, so i'll discuss with the dealer.

 

OK so I'm very new to all this. I live in southern california and basically have great weather year round. I live in orange county and work in San Diego. Yes it's crazy for some in so cal to do this. I drive 180 miles/day. I bought my 2009 prius Jan 11, 2009 and since then have accumulated 50K+ miles. Up until Dec 2009 i was maintaining 46mpg between fill-ups and I was happy enough because 1) used to drive a truck and 2) lead-footed @ 80mph. I now constantly average about 40mpg and it's getting to me. I checked my oil and it is over-filled then slightly drained, checked my tires they were at 40, changed my engine air filter, etc... One thing I didn't do was check the battery. So i ask, where is the thread that has instructions to see the data for battery charge? Could it be my battery? my driving hasn't changed since i got the car, so does my problem lie in this thread? what are some other things to try and help me with my mpg? this seems to be an ongoing problem with a lot of prius owners, is it still really worth it, did i make the right decision? i hope i did... Please help!

Carl

 

It's not likely to be your battery after only one year, but the thread you want is below.

http://priuschat.com/forums/newbie-...-test-battery.html?highlight=maintenance+mode

Thanks to Richard Schumacher

 

I would ask do you get your gas at the same station all the time? I bought some crazy cheap fuel one day and saw a large drop in mpg's from 47 to 42. Different station the mpg's are going back up. It was a cooler week for So. CA but not that cool.

 

So, still confused.... I do get gas from the same Shell station by my house. As i drove to the OC today maintaining speed between 75-80mph i again only got 37.5mpg for 75 miles. Now it's starting to worry me that i have a bigger problem. any suggestions for me to check?

 

So i tried this technique and found that my battery after 1 year is as follows:
Unload: 12.4V
Load: 12.1-12.2V
Charge/Start: 14.2 V

I don't think my decrease in mpg is due to the battery. Has anyone else experienced a decrease in mpg, about 10mpg, and fixed the problem yet found the cause?

 

Hmm. Has *anything* else changed or happened? New route? New driver? Ran over a tree trunk? 300 lb guy joined your carpool? It's funny sometimes what people won't think to mention.

 

I'm still the driver and take the same route. I may have fluctuated my weight about 10lbs hahaha but i'm 5'10" 185lbs. Ran over general pot holes in so cal but nothing significant. took the car to the mountains for snowboarding 2 weeks ago, since then i leave the chains in the trunk compartment area. i doubt that a 7lb weight would drop an additional 7-8mpgs. I replaced the tires to Michelin X from costco with psi at 40 on all 4 tires. changed the engine air filter yesterday. i know i'm lead footed at times but 80mph is what i always do and i consistently stayed at 45-46mpg for 11 months. *frustrating*

 

Did you just say you have new tires? Just about everyone has reported a significant mpg drop after fitting new tires. Give them a few thousand miles to break in and you'll probably see the mpg crawl back up. Same is happening with my Primacy MXV4s.

- D

 

it's been 5k miles w/ an oil change already, i should've seen the changes already if that's the case. could that be?