Questions about battery/mpg/possible problem

I personally don't think there is anything wrong with your car. Mpg can lower due to short trips also, especially in the cold. For me, I had over 50 for the first 2-3000 miles or so (with warm weather and long highway trips), but now it is probably in the low 40's since I take a lot of 5-10 min drives and it is cold.

The battary charges and discharges depending on how you drive and the roads, may be you are coasting more these days even you don't think you do

I might be wrong, but by reading your post, I don't see any trouble.

 

The good news: There's probably nothing wrong with your car.

The bad news: It's going to do this every winter.

You are right about winter gas, it gives us poor mileage. It did the same thing with your previous car but like most of us you didn't notice. As previously stated the engine needs to run more to keep the catalytic converter warm, keep heat in the car, etc. Even a mild winter is cold enough to make a big difference. I have seen a 5 to 10 MPG drop since Summer. But it will come back up again.

 

I’ve also noticed a drop in MPG (from 48/49 to 43/44) when I use Shell gas; it goes up again when I put Mobil.
(Always use the same Shell or Mobil station and have tried almost all the pumps in each one)

 

Another possibility: Low tire pressure.

This happened to me a few months back. I saw my MPG drop to the low 40's for no appearant reason. It turns out I had a very slow leak in one of my tires. Now I check the pressure regularly

Altho' I don't recall seeing an increased SOC as a result.

<Oops! Sorry, just re-read your post, it's not tire pressure>

 

I vote for typical cold-weather behavior, which would explain both the lowered mpg and the higher battery SOC.

Cold weather (or more properly, demand for cabin heat) causes the engine to run more. This lowers your mpg and also leads to the battery being generally more charged. Additionally, cold weather means the battery is colder when you start up in the morning, and a cold battery is less efficient and therefore produces lower mpg.

None of this is bad for the car, and none of it is a malfunction. Of course, lower mpg is "bad," but only in the sense that the car burns more gas in cold weather.

It will go back to the way it was when summer returns. Just be glad you don't live in a really cold climate, where you could, under the "right" conditions, see mpg as low as 30.

 

<div class='quotetop'>QUOTE(Etel Rose @ Jan 1 2007, 03:31 PM) [snapback]369350[/snapback]</div>

If you aren't sure ....I say take it to the dealer. I noticed an electical smell in my recently purchased '05 and they said they needed to change the computer. Bottom line for me is that this is a unique machine and if you think there may ne something wrong...tale it to the folks who know best. No flames please, I know the dealership isn't perfect.

100 mile a day communte for me and this site has been fantastic....thanks to all.

 

<div class='quotetop'>QUOTE(Etel Rose @ Jan 1 2007, 06:31 PM) [snapback]369350[/snapback]</div>

Mine shows green bars most of the time since it got colder. As someone else said, the engine runs more to give you heat and that keeps the battery more fully charged than in the summer. I just got back from a trip to Florida and while down there, with temps around 80F, I hardly saw green bars at all.

 

I wouldn't rule out the batteries.

There's almost 36,000 miles on my car. It's gone through 3 summers and this is its 3rd winter. The first year it averaged 48 to 49 mpg. The second year was 45 to 46 mpg, and right now it's down to 39 to 40 mpg. Not so long ago in a post I bragged that the car had never experienced lower than 44 mpg. Now it never gets that high. It's been serviced at least every 5000 miles by Toyota. I've been on this forum since late 2003 and have followed all suggestions aimed at addressing mileage problems.

I've read where Prius battery failures are very rare, but I've not read anything on the topic of battery degredation. With a loss of 10 mpg after 33 months but with everything about the car seemingly working just fine, I'm beginning to believe my battery simply does not yield the same current per given time as it used to. Assuming that's the case, the internal combustion engine has to do more of the work than before. I've never known any other of my rechargable batteries to not degrade over time. I can't see why the Prius batteries would be any different.

The battery does show green bars when, for instance, I drive from the heights to the valley - a change in elevation of of about 1000 feet - takes about 20 minutes), under typical driving conditions it shows some number of blue bars, and when I drive from the valley to the heights it typically gets down to 1 to 3 purple bars. So .. The battery display doesn't seem all that different than when I first bought the car.

This mileage thing is pretty dissappointing. I'll be taking the car in soon and will report the poor mileage as a problem that needs to be corrected. I would imagine the Toyota service department would have some apparatus for checking the effectiveness of the batteries. If so, I'm hoping they'll make that check and let me know the results.

 

ya your mileage is normal stuff. noticed the drop in Nov??? from a tank that was filled up AFTER Oct 15th???

i ask because i live a hundred miles north of you and our area went to winter formula gas on Oct 15th. that is an instant 3-6% drop in gas mileage. so boom, thats 1-3 mpg.

average increase in air density is actually what will cause the greatest change in your mileage. that can be as much as 15% in the winter but you are right, the weather is mild here, but the air density is not, much higher humidity can affect mileage as well... something about the unfriendliness of burning wet air as opposed to dry air... but around here, that is another 2-5 mpg and much more on those occasional cold snaps.

increased rolling friction is another lesser factor caused from driving on wet pavement... amount varies by how much rain we get but during those very heavy storms we had when standing water on the freeway was present, i could see my instantaneous mileage drop AS I DROVE THRU the puddles. that is a huge cost getting back up or maintaining speed.

colder weather does mean slightly lower air pressure on your tires, its a good time to check your pressure. best time is after the car has sat overnight early in the morning

so, should you get less mileage?

ya you should.

in the summer my minimal average is 55 mpg, runs as high as 62 mpg for a tank. in the winter i run 49-52 mpg and only because i completely block my radiator from getting any air flow (helps keep the ICE warm) im pretty sure that will boost your mileage at least 2-4 mpg as it has mine.

after a few weeks, which included several trips of more than 50 miles of mixed driving, i have yet to see a water temp of over 211ºF, (dont have CANVIEW so cant monitor engine and converter temps which is the better way to go) and at that temp, the circulation fan never comes on so its got to be in the normal range.

also, if the temps are in the high 30's or lower, my max water temp usually doesnt get above 175ºF and i know that is not anywhere near warm enough. (thermostat does not open until 190-195º) on my short commute. that lowers my mileage to 39-44 mpg. same trip that gets me 60-70 mpg in the summer time.

 

Dave's post above (not the whole thread) should be in a sticky post for everyone going into their first winter with a Prius and wondering about mileage!