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Declining mileage in 2008 toyota prius

I also have this situation. My on-board mileage calculator reads 45 - 50 mpg around town during the summer and then declines to 27 to 35 mpg for the coldest Indiana months. Recently it warmed from 15 degrees to 35 over night and the mileage jumped from 30 to 42 mpg. I cannot buy the gas difference reasoning as this was on the same tank of gas. My wife also bought the same model, at the same time and her mileage only declines 5 mpg. I drive her car occasionally and get the same higher mileage as her - so much for the lead foot theory!. Toyota seems as puzzled as I do. Their diagnostics say that everything is in range and I should get over it. Do I have a loose connection that shuts off the battery circuit in the cold weather? Do I have any lemon law options? Is this a terrorist plot? Would keeping the battery warm overnight help?

The real question is, what is the ACTUAL gas mileage you’re obtaining, based on miles driven (from the odometer) and gallons of gas used (as measured at the pump).

It could well be that your actual gas mileage is the same as your wife’s, but for some reason there’s a difference in the system that calculates and displays the “instantaneous” mileage. I wouldn’t get worked up about it until and unless you actually measure your mileage and find a real discrepancy.

This is just what happens when batteries are cold. (And your engine is cold. All cars get worse mileage in the cold, even hybrids.)

Yes, it would help if the batteries were kept warm but it’s probably not cost efficient to do this.

OK, jesmed, you may have a point. I did this once two years age but I will verify the mileage the next time I fill and drain the tank. Toyota mentioned that their gas tank is actually a bladder and so could be the problem.

Has any one else checked this out and found it to be a problem.

PS the mileage reading feature I refer to is an average of several (~100) miles and not an instantaneous mileage.

You Need To Replace The Whole Outfit With A Bicycle, But I’m Not Sure You Could Play The “Lemon Law” Card On A Bike Manufacturer. Will This Hybrid Car Thing Ever End ?

Whatever you’re saving in the summer or the winter isn’t worth the anguish of owning this car.


Well Goldwing, you may be right. My power tool batteries really suffer in the winter in my garage.

Regarding cost effectiveness, I calculated the use of a 65 watt heating pad for eight hours (overnight)to cost $1.80 a month. I have averaged 50 miles a day. If the gas mileage would be increased from 30 to 45 mpg, at $3/gallon, it would save $50 per month during the cold months. I may give this a try!!
Click/ Clack - jump in anytime!!

Hybrids are one of the main solutions to the peak oil / climate change fossil fuel problem. What I want to know is why aren’t hybrid batteries mandatory in all vehicles especially in mail trucks, school and transit bus’s ?? !@!

It won’t be cost effective. Your biggest factor in winter mileage is the fact that gas engines run richer in cold weather. Contributing factors are thing slike thicker lubricans. Warming the battery won’t help this.

But feel free to try and let us know how you make out.

By the way, the brothers rarely visit here if at all.


And that may be a good thing. If all vehicles were mandated to be hybrids, all would be more expensive. Fewer people would be able to replace their beaters with new vehicles. They’d drive them longer and we’d have more old beaters on the road that might have been replaced with newer, cleaner, more fuel efficient cars if hybrids had not been mandated.

They’re Perfect For People Who Believe That Climate Change Is Being Caused By Fossil Fuel And That By Driving A Hybrid They’re Actually Making A Difference, With Or Without MPG Problems.

For the rest of us, not so much.


Unfortunately, the laws of physics don’t care what some people choose to believe or disbelieve. As far as several thousand years of human inquiry can ascertain, the laws of physics are immutable and will govern the outcome of our grand experiment in unleashing vast quantities of CO2 into the atmosphere in an incredibly short period of time (geologically speaking)regardless of any human opinion.

Virtually all of the science now supports the conclusion that more CO2 released into the atmosphere = faster overall warming of the planet. In the science community, there are practically no climate scientists left, save a few bought and paid for by oil companies, who argue otherwise.

Disbelief in what has been proven as definitively as is possible in an uncontrolled global experiment will not shield any of us nor our children nor grandchildren from the results of our grand experiment. Nor from our responsibility for the results of our action (or inaction).

You’ve Been Watching AlGore Movies Or Drinking Al Gore Kool-Aid. I Find More Good Than Bad Associated With Global Warming (Oops, Sorry - Climate Change). Bring It On, Please.

When the Earth started cooling again because of natural cycles, global warming was repackaged as climate change. My heat bills have been steadily increasing over the past couple of decades. Some people who are wet behind the ears are too eager to accept natural weather patterns as climate change. That’s fine, but don’t screw everything up for the rest of us.

These climate change folks have made a fortune from this Man-Made Climate Change Histeria and have been found to falsify their information.


“…don’t screw everything up for the rest of us.”

Oh, don’t fret, now. There’s plenty more oil and coal and gas for us all to burn to our heart’s content.

It’s our grandkids and all the generations after them who are going to be screwed by climate change.

You need to source your information from some place other than TV news blurbs.

My son is actually in the climate field (meteorologist and climatologist) and I’ll ask you what he’s brought up many times. He does not get involved in these discussions withe people who are not in the field because as he put it, when someone has the option of listening to a 2 minute news blurb with dramatic pictures or poring over charts and scientific papers that are beyond their comprehension then which option do you think they will take? That’s right, the easy way out.

You state (as does TV) that “most scientists believe in man-made global warming”.
Where do you source this information from?

You state that the few scientists who state otherwise are on the payroll of Big Oil.
Where do you source this info from and can you name even a few of them?

Since my son is in the field and knows many other scientists in this area neither he nor his cohorts have ever been polled on this issue and know no one who has.
This begs the question; who is doing the alleged polling and who are they polling?

If “global warming” was true, you wouldn’t be having issues with your hybrid batteries.

See video:


I don’t watch TV news; I read scientific analyses and papers which, having an advanced engineering degree with an emphasis on thermodynamics, I actually do understand :wink:

But since you asked, here’s an excellent one-stop shop that explains what is currently known about global warming:

As for your question about who is being polled, read the answer to “Most Used Skeptic Argument #3: There Is No Consensus.”

As someone has pointed out, “global warming” should really be called “global weirding.” Even though the AVERAGE global temperature has been rising, bad/cold winter weather will still occur in North America and other northern climates. But if you look at what’s happening closer to the equator, they won’t be so lucky. They’ll be experiencing more fun events like severe drought.

So you’re saying a degree in thermodynamics means you can speak with authority about the climate?
Since you did not answer most of the questions I posed I’ll ask this.
Are you aware that most of the “expert climate scientists” that are often quoted on this issue are, like you, not climate scientists at all?

Are you aware that the IPCC report (the template used to push this issue) was written by many “climate scientists” who hold PhDs in Economics, Sociology, etc and know less than zero about the climate field? Few of those 2500 are climate scientists at all.

Lastly, let me ask this one. While I’m not going to dredge up the entire report let me throw a few paraphrased comments out of this report out there to see what your opinion would be.
“August was the hottest month on record…”
“Heat related deaths had skyrocketed with 3 dead in Chicago and even more in NYC where 3 children died when they fell from fire escapes while trying to find a cool breeze…”
“Average temperatures were the highest they had been in over a generation…”
"The waters of the Gulf of Mexico were much warmer than usual, leading to increased hurrican strength…“
The Bering Glacier in Alaska was sprouting rivers, calving countless icebergs, and has lost over 600 feet of its depth…”

Do you consider those comments the sign of global warming?

Apparently you haven’t read “Unstoppable Global Warming, every 1500 years” by Dr. Fred Singer. He refutes, with evidence, almost every thing you spout about Global Warming or whatever the hoaxers are calling it these days.

To those global warming / climate change deniers:
I bought the hybrid Prius to do my small part to provide more time for my progeny to invent fusion power to overcome the catastrophe that global warming / climate change will be.
Many, on the other hand, are descendant from a long line of morons that include the isolationists prior to World War II, people who see Jesus in the asshole of a dog, the investors in Bernie Madoff and owners of 6000 pound gas guzzling SUV?s.

Which is more likely?
A majority of scientists have collaborated and concocted this huge plot to defraud the world community by falsifying data and photos.

Oil, Natural Gas and Coal companies, who have enormous financial resources to influence media, politicians and scientists, are spewing false information to primarily preserve their own jobs and stock options.

Why do we believe someone with such a clear conflict of interest and then vote and behave just as they want us to?

If you dare, read this paper written by someone who has no axe to grind.<0499%3ARTSOGW>2.0.CO%3B2

Do not rely on Uncle Goober who remembers that it was cold last week.

If you have children and grandchildren, join the party just in case you?re wrong.