Falling gas mileage

I took delivery of my Prius on 9/9/05, still hot summer weather in the 90s here, and was very smug that I could get 51 or 52 mpg as a novice Prius driver. Now that the daytime temprature is in the 40s and 50s and we have winter gas I get 47 or 48 mpg. BTW I live in an area where it's pretty easy to get good mileage due to the light traffic.

 

Normal behavior check out the block heater threads in Performance Mods and the Decreasing MPG thread in Fuel Economy for information on blocking the radiator during the winter. It is going to be a lot colder where you are than I. If you have not done so check out the threads on getting snow tiers, many have suggested you may need them. For the 5 days or so of snow we get in the Northwest I just drive my old Ford Explorer.

 

Moved to fuel economy forum.

 

:huh: I averaged 44-or better mpg this past summer..down to 34-36 this winter.
I live in Illinois and its been cold. Thanks for the other posts.

 

same here I am down there as well, do you not think this is some kind of design flaw that Toyota should come up with a fix for? Since they advertise such high mpg that no one that drives normaly gets that they would at least want to give you a free block heater or some device that would help in cold weather. I saw a news report on all the flack Toyota is gettting over the Prius and its less than advertised MPG . Its a good car but....the truth will or should set them free and the truth is not 60mpg

 

Weather is a design flaw? I think not. Look how the EPA does these tests. We are talking summer no wind resistance etc etc etc. They are there for purposes of comparison only! You are looking at mpg enthusiasts. You can not compare those people to the EPA. Folks like that are driving these cars to the limit. You may want to join in. There were 4 folks that got 110 mpg in August in Pittsburgh. You could do the same if you try. Toyota is not responsible for the EPA numbers, they are done by the EPA. Oh bye the way I aspire to that record and will do what I can to meet the challenge! Now how do you get those back seats out?

 

Dogtrainer, Toyota has to, by law, post the EPA mileage numbers on their cars. Every manufacturer HAS to do that. I think that, especially in the Prius's case, they'd rather not. As we've all seen from reading the posts here at PC that YMMV (your mileage may vary) rules the day. This car has great potential for exceptional fuel economy as well as pretty disappointing numbers. It's all in how you drive it. While that's really true of any car it's even more so in the Prius.

BTW, the EPA test is done at 72 deg F on a level track and they don't start measuring until the car has reached cruising speed (ie, no acceleration). They then determine the amount of fuel consumed by measuring CO2 output.

If I misstated anything somebody correct me. I don't wanna spread misconceptions but this is how I believe it works at a very high level.

All of those conditions are obviously unrealistic all of the time. Especially the last. I'd love to jump to my cruising speed without have to invest the energy to get me there. A'int gonna happen though.

 

wisconsin does get pretty chilly in the wintertime.

the battery is the main reason you see lackluster performance in the wintertime. it doesn't like being cold. same reason your regular car doesn't want to start some days- cold battery.

plus, driving on snow and slush is hard on any car. you'll notice any car has a marked drop in fuel economy in the winter. not just the prius. 38 may be bad for the prius, but at least it's not down to single digits like my last car was in the winter!

 

On top of that many places put up to 10% ethanol in the gasoline during the winter. Since Ethanol has a lower energy density than gasoline fuel economy will take a dip.

 

yeah, good point. i forgot to mention winter formulation gasoline.

 

IT IS NOT A DESIGN FLAW.

It's called the weather. It's this wonderful thing we have in our part of the world call the season of winter. Pick any car on the road. That anycar gets SIGNIFICANTLY worse than EPA mileage in the winter time, and during summer months, may not get EPA rating because of driver skill, terrain, traffic patterns.

The news report you saw was bogus...

This is not a problem with the Prius, or with Toyota, or anyone else except for the DRIVER... if the driver is disappointed, it is because he set his expectations too high.

EPA numbers are not meant to be a definitive measure of what your mileage will be. It is a standardized test meant for comparison purposes only.

that being said, it *IS* possible to get decent mileage in the winter, but it really depends on your driving conditions, and driver skill.

 

Nice to get confirmation I'm not the only one. Got mine in July, too, in NY, was getting near 50 mpg on long drives, 47 on my usual commute. It's now ~20-30 degrees F, and my mileage is down to 37 or so. A BIG factor is the usual length of your drive. My commute to the train is only about 15 minutes, so most of my driving is with a cold engine and battery in winter, which, coupled with winter fuel formulation really kills my mileage. But like the man said, 38mpg in a nice, midsize car STILL far and away beats the 22mpg I was getting in winter, in my Civic with a standard shift on the SAME commute. And the Prius warms up much faster. And handles better in the snow. But I DO have to complain about what a pain it is to gas up when it is cold--I cam only pump the gas very slow, with the nozzle half out of the fill--and even then it spurts out at the end. Ugh!

 

bought mine in jan 05 and found in cold weather here in lexington ky i get
about 38 mgg.At first i wasnt verry happy but learned to live with it.now im
happy to get 38 mpg as my tundra only got about 10 mpg when it was cold

 

Prius runs so cleanly that evaporation of fuel is the largest potential source of hydrocarbon pollution. The fuel bladder reduces fuel evaporation, but this feature does not work correctly if you top off. Topping off also greatly increases the chances of fuel spitting.

Manual per-tank MPG calculations are often inaccurate in Prius because (the bladder, again) you don't know accurately how much fuel is in the tank when you start a fillup; all you know is how much you put in, which is not the same as how much you burned since the last fillup. The MFD MPG calculation in contrast is always very accurate because it uses the amount of gas flowing through the injectors. The only use for manual MPG is to track lifetime MPG, and that is most accurately done using the distance and MPG figures from the MFD.

An MPG decrease in winter is just physics. It takes more fuel to heat cold air, and more fuel to heat up the engine to correct operating temperature. Short trips in cold weather are MPG killers in any car; the Prius display just makes it obvious.

 

I agree that length and type of commute is very critical to your performance! I've had my 04 since November 2003 and my normal MPG in summer is 50 - 52 and in winter is 46 - 48. This is not nearly the drastic drop that some have seen but my commute is a very consistent 40 miles one-way of freeway at mostly freeway speeds. I've kept records since the day I bought it and my current overall MPG is 49.5.

 

My '02 Classic gets better than 50 mpg in the nice sunny weather. Even with AC! Now that we are below freezing here in NJ the car is only getting about 41-43 mpg

Part of the problem is a lot of short trips, and there is not much that will help that. Don't think a block heater would help at all as my car lives in the garage and never gets that cold at night. Where a block heater would help would be if my wife could plug it in during the day where it sits out by the train station. When she gets to the car around 6pm it is frozen solid. Unfortunately, there is no place to plug it in.

Guess we will just wait till warm weather to get the mileage back up.