Foo - Prius mpg strangeness

I bought an '08 Prius in September and have been very happy with the car. For the first couple
of months I was able to get 52 mpg fairly easily with a combination of city and highway driving
without having to pay too much attention to how I was driving. Now for some strange reason I
can barely get 42 mpg. I don't think anything has changed with respect to my driving style. At
first I thought it might be that I've been using the heat more often since is colder out now, but
a 10 mpg seems excessive. So for the last week I've been driving it around without using the
heat at all and the performance hasn't changed.

Can anyone think of what sorts of things might cause such a drop?

winter gas.

winter gas.

"winter gas" ?

oh, so that's why it is so cheap ($1.59 to $1.93) lol.

ok, so seriously now...

You have too many bodies in the trunk. More weight means more power to get moving. Time to dig a shallow mass grave!

You have too many bodies in the trunk. More weight means more power to get moving. Time to dig a shallow mass grave!


I checked just now and found that the bodies mysteriously disappeared. So it must be something else. I'm kinda glad they are gone because they kind of smell.

Anyone out there on foo who isn't currently drunk?? :lol:

Anyone out there on foo who isn't currently drunk?? :lol:You must be new here.

winter gas.

Yep, we recently went to a 10% ethanol gas and my mileage dropped substantially. Also, the car is generally less efficient in the colder months as more energy is needed to warm the car and keep it warm. Also the battery is less efficient when cold. All that adds up to a drop in mpg in the winter. My year round average is about 45 mpg. More in the summer and less in the winter.

^^^ What he said.

PLUS:

Check your air pressure in your tires. Hot weather makes air expand, cold weather does the opposite. If the psi is not up to par, your gas mileage will be affected. Think about how it is to ride your bike on low tires.

"winter gas" ? ok, so seriously now...

He is serious.

In Winter the temperature differential and the higher ambient humidity causes condensation on the inside of the underground storage tanks (and the tank in your car), putting a higher water content into the fuel. Cars don't run well on water.

You might try pouring a small bottle of rubbing alcohol into the next tank the next time you fill up.

He is serious.

In Winter the temperature differential and the higher ambient humidity causes condensation on the inside of the underground storage tanks (and the tank in your car), putting a higher water content into the fuel. Cars don't run well on water.

You might try pouring a small bottle of rubbing alcohol into the next tank the next time you fill up.

I thought he might have been joking only because the drop was quite large. I thought a 10 mpg drop meant something was wrong with the car. So this winter effect really can make that much difference?
(assuming the tires are fine)

All of it adds up to the big drop.

My I think it is cold weather related. If i were you i would post this same question at Gassavers.org they will help ya out alot more.

^^^ What he said.

PLUS:

Check your air pressure in your tires. Hot weather makes air expand, cold weather does the opposite. If the psi is not up to par, your gas mileage will be affected. Think about how it is to ride your bike on low tires.

That is what I was thinking.

My I think it is cold weather related. If i were you i would post this same question at Gassavers.org they will help ya out alot more.

Oh yeah. The word of Foo is trash. Never mind us. We don't drive cars. Us bike people don't know squat about cars.

Oh yeah. The word of Foo is trash. Never mind us. We don't drive cars. Us bike people don't know squat about cars.

seriously....

sorry for my ignorance but what is foo I have seen this a few times already. Also I didnt mean it like that people at gassavers are just crazy when it comes to gettin the most out of mpgs

"Foo" is the section of the forums you are posting in right now.

Referring someone to another site when she is getting answers here (from people who know cars) is kinda like telling someone at McDonald's to go to Jack-in-the-Box. Plus it makes us feel like you are doubting our word. She came here probably because she knows that we have some car fanatics as well as auto mechanics by trade here. Plus she knows us and might be comfortable asking here. But it's all good. You were only trying to help. No hard feelings.

And welcome to Foo. :)

^^^ hehe I decided to pay my membership fee here after getting awesome answers on Foo to all sorts of random stuff. I've even posted some of my mom's questions in here and got 1/2 page of answers in less than an hour. So now she always jokes that if she has a question about something, she will ask me to post something here. lol.

For those of you just discovering the magic that is Foo: You will also experience totally random, seriously wrong, unseriously wrong, wry, sarcastic, plain silly, deluxe silly, disturbed and undisturbed answers to any given query. The key is to take it all in stride. We all come for differing reasons, yet all leave with the same thing: Entertainment, education...and almost always a smile. :)

...and nausea.

...and nausea.

So eat something. :p

Not sure about california but here in oregon theres is ethenol in the gas year around

Almost all gasoline sold in the U.S., that standard stuff we all know (87, 89, 92/3/4/5. etc.) has ethanol in it. Usually about 10%.

My motorcycle doesn't even get 42 mpg you idiots.

I bought an '08 Prius in September and have been very happy with the car. For the first couple
of months I was able to get 52 mpg fairly easily with a combination of city and highway driving
without having to pay too much attention to how I was driving. Now for some strange reason I
can barely get 42 mpg. I don't think anything has changed with respect to my driving style. At
first I thought it might be that I've been using the heat more often since is colder out now, but
a 10 mpg seems excessive. So for the last week I've been driving it around without using the
heat at all and the performance hasn't changed.

Can anyone think of what sorts of things might cause such a drop?

Put air in the tires. Max out the PSI for best mpg.
I get 43 mpg in my 2002 Echo.

My motorcycle doesn't even get 42 mpg you idiots.

On the other hand, I'll bet your Prius doesn't go 0-100 mph in 8.3 seconds.

Ok more than a two word answer.

In the winter they add more light compounds to gasoline like MTBE ethers and propane (and a lot more stuff). The claimed benefit is that your car will start more easily in colder temperatures. These compounds decrease the fuel BTUs by thinning it and displacing the fuel component. The bottom line is that you get less mileage. Essentially, there is less "gasoline" in the gas.

For cynics such as myself, I think they would sell you winter gas all year if they could get away with it, but it would be too volatile during the warm months and potentially unsafe to store. I never obtain fuel information from the fuel company, only from independent sources (if they exist).

The other arguments are true. Tire PSI, battery efficiency, and oil viscosity all change with ambient temperature. I tend to see between a 10% and 20% decrease in fuel efficiency in the winter, depending on which state I buy the gas from. NY is one of the worst. Ohio winter gas seemed to give me summer-like MPG numbers.

YMMV (of course)

Ok more than a two word answer.

In the winter they add more light compounds to gasoline like MTBE ethers and propane (and a lot more stuff). The claimed benefit is that your car will start more easily in colder temperatures. These compounds decrease the fuel BTUs by thinning it and displacing the fuel component. The bottom line is that you get less mileage. Essentially, there is less "gasoline" in the gas.

For cynics such as myself, I think they would sell you winter gas all year if they could get away with it, but it would be too volatile during the warm months and potentially unsafe to store. I never obtain fuel information from the fuel company, only from independent sources (if they exist).

The other arguments are true. Tire PSI, battery efficiency, and oil viscosity all change with ambient temperature. I tend to see between a 10% and 20% decrease in fuel efficiency in the winter, depending on which state I buy the gas from. NY is one of the worst. Ohio winter gas seemed to give me summer-like MPG numbers.

YMMV (of course)

But Grumpy, you think the Big Oil Companies are manipulating world oil prices. Grumpy's motorcycle goes 0-100 in under 8 seconds by the way.

I get 15 mpg in my unimog/

Can anyone think of what sorts of things might cause such a drop?

Yes, winter... All cars get worse MPG in the winter than they do in the summer. However, a 10% - 20% drop in fuel economy on a car that gets 16 mpg - 20 mpg is a lot less dramatic than one that gets 40 mpg to 50 mpg.

As someone else noted, your choice of fuel and winter blends with additives for the cold weather will also impact your fuel economy, with or without ethanol. In fact, I avoid ethanol (E85 or the "may contain up to 10%) as much as possible as it reduces my truck's already poor fuel economy by another 10% - 15%.

You must also account for how cold weather affects the mechanical parts of your engine. It takes your car longer to warm-up in the winter and your EFI / ECU system tries to compensate for that by using higher RPMs for cold engine idle time and, well, an engine idling at higher revs for a longer period of time burns more gas. Moreover, if you live where it's really cold and let your car warm-up before hopping in to drive off and/or have to clear snow or ice off while the car idles... well, you do the math.

I don't own a Toyota hybrid (or any hybrid for that matter; I ride a motorcycle to work year round and, yes, my MPG is worse than a Prius) so I'm not sure what ambient outdoor temperature Toyota has set the engine auto-stop at, but I'll bet it's somewhere around 35°, therefore your engine is simply running more when it's cold. Additionally, hybrids are more sensitive to heavy electrical draw and in the winter we drive in the dark more often with headlights on and folks run heaters and defrosters at higher power levels and those things make engines work harder and may also impact your engine auto-off features.

Tires have also been mentioned and, yes, you do need to adjust your tire pressure when the temperatures change with the seasons. Additionally, cold tires don't roll as efficiently as they do once they're warmed up and I'd bet that the special tires used on hybrids are even more sensitive to cold weather.

Finally, there's the environment outside of your car. Cold air is more dense than warm air. Hence, there's more aerodynamic drag working against your car (same goes for cycling, eh?) and the Prius is perhaps one of the most aerodynamically sensitive cars on the road when it comes to MPG. Even putting a bike on a hitch mount bike rack will drag down your fuel efficiency far more than what you'd see on cars that higher coefficients of drag. Add in winter weather head and cross wind effects and, well, again you can do the math.

But Grumpy, you think the Big Oil Companies are manipulating world oil prices. Grumpy's motorcycle goes 0-100 in under 8 seconds by the way.that is quick

But Grumpy, you think the Big Oil Companies are manipulating world oil prices. Grumpy's motorcycle goes 0-100 in under 8 seconds by the way.

They won't get me as long as I wear my aluminum foil helmet.



here's some drag times on the GSXR-600

1/4 Mile ET: 10.939
1/4 Mile MPH: 124.260
1/8 Mile ET: 7.050
1/8 Mile MPH: 102.560
0-60 Foot ET: 1.784

My motorcycle doesn't even get 42 mpg you idiots.

try one of the bavarian ones and frederize yourself further.

On the other hand, I'll bet your Prius doesn't go 0-100 mph in 8.3 seconds.

Actually, I'd bet the 08's can. Don't diss electric motors. They can have more torque than 10L V18.

And the reason why the gas mileage is low is because it's winter. My parent's have Prius and it's the same way. Nothing to worry about.

Actually, I'd bet the 08's can. Don't diss electric motors. They can have more torque than 10L V18.

And the reason why the gas mileage is low is because it's winter. My parent's have Prius and it's the same way. Nothing to worry about.

I'll take that bet!


(could use some extra money) :D

Actually, I'd bet the 08's can. Don't diss electric motors. They can have more torque than 10L V18.

Read more carefully. Not zero to sixty Hickey. zero to ONE HUNDRED mph. Prius's don't do that. Some Ferraris can. Some Ferrari's, not most.

I'll take that bet!


(could use some extra money) :D

Have you ever floored a Prius??

Read more carefully. Not zero to sixty Hickey. zero to ONE HUNDRED mph. Prius's don't do that. Some Ferraris can. Some Ferrari's, not most.

I got my parent's Prius up to 80. I'm sure it would have no problem doing 100

I got my parent's Prius up to 80. I'm sure it would have no problem doing 100

You really do have a reading comprehension issue. I know Prius's can go 100 mph kid. The 0-100 mph stat addresses how QUICKLY a vehicle can accelerate. Get it?

ok here's an 06 bone stock Prius on the 1/4 mile

1/4 Mile ET: 17.810
1/4 Mile MPH: 77.910

http://www.dragtimes.com/Toyota-Prius-Timeslip-8038.html

Have you ever floored a Prius??

I've flipped a few Prius owners when they are playing on the left side of the interstate.

K1200S needs some room ... move out of the way!! (and still gets better mileage than p=cads bike)

I'm still willing to entertain the possibility that they upped the horsepower in the 08 model by maybe 300%, but I would not take that bet :P

On the other hand you can cruise in a Prius @ 85mph and get 40 mpg+ with two bikes on the roof. How great is that?

Our next car will either be a Prius, a future Honda hybrid (they have a new one coming out in the first half of 2009) or a used 1989 Ford Taurus with 189K miles, depending on whether we get the Great Depression II or not.

it hardly snows by you though pcad, you can ride the moto most of the year...

it hardly snows by you though pcad, you can ride the moto most of the year...

I can't ride my m/c when it's below high 40's Andrew. Too cold for me. I can ride my bicycle when it's 12ºF. But it's chilly.

But yes the roads are mostly dry and free of ice here most of the winter. Not today however. And we do get winters here where it's snow covered for much of the winter, I've had 30" of snow in my yard once or twice. I'm starting to think this may be one of those winters. It does snow here quite often when it's raining 30 miles south of here. All the time in fact.

twelve degrees.

trainer for me.

That's amazing. It's 32ºF here. Wow. You do live in the Snow Belt. You are totally F'd, aren't you?

Ok here's what it's like going 0-100 in the gixxer.

I spin up the throttle to about 5000 or 6000 and then let the clutch out just hard enough to keep the front wheel down. Then I slowly pin the throttle open and lean forward. Once the engine gets to about 14000 I kick it into second. Then I hit 100 mph.

in second gear.

That's amazing. It's 32ºF here. Wow. You do live in the Snow Belt. You are totally F'd, aren't you?

lol no not today. I was responding to your post! it's 29 right now.

I can't ride my m/c when it's below high 40's Andrew. Too cold for me.

I'm good to about 18° here in Atlanta; however, on days like that it's not me that gets too cold: Gerbings electric jacket liner & gloves + Fieldsheer one piece, thank you very much. Instead, after sitting outside being cold-soaked in sub 32° temps for 10-12 hours it's my motorcycle that doesn't usually feel like starting. I've thought about selling my '98 CBR1100 and getting a BMW or ST1300 with their full coverage windscreens and better electrical systems (the Gerbings stuff is really hard on my Honda's minimalist electrical system) but I'm just not "there" yet in terms of coming to grips with old age.