Colder weather has zapped my mileage to 44mpg

What was your expectation? EPA combined 50 MPG? Drive it for one year round and see what your average ends up with. I think you will get less than 50 MPG because you drive faster than EPA test. If you can get 50 MPG average, it is even better.

I mentioned tunnel vision because your emotional replies are based on the "heat of the moment" (current MPG). I still think something else happened to your Prius other than the cold weather. The MPG drop is unusually high. I did 65-72 MPH (depending on the hills) for 10 mins on the highway on the back to home. I got about 48 MPG on both of those two 5 mins intervals. Your 38 MPG at average 68 MPH is low. Maciej_S got 39 MPG at 81 MPH. According to his test, you should get more than 47 MPG for a gen 3.

Either you are going faster than you admit (you can idle to bring down the average speed) or something is wrong with your car.

Do you have a bike rack or roof rack?

 

Replaced why?

Is this the same dealer that told you the winter MPG hit was fixed? I'm not sure I'd believe anything he said.

 

Hi guys, I think the drop in mileage is due to the heater being run, during the cold months. The engine stays on longer, because you're trying the heat the cabin (and for good reason), actually the engine will stay on even when you're stopped at a light. There's probably not much you can do, unless you're willing to bear the cold (which I wouldn't recommend) since you want to comfortable in your car during the trip.

 

My expectations were stay above 50 for lifetime. I remember discussing this with "a priori" and others. Back on summer, he loaded his Prius with people and stuff and went for a hwy trip with rain, against the winds sometimes, and A/C on all the time. He was not going particularly slow either, his cruising MPH was about 72 if I recall correctly. He also has the Prius with 17" wheels. His overall MPG was about 50 or slight higher in that trip... than I thought... I will drive by myself only in my hwy trips, 15" wheels, similar speeds, so 50+ MPG calculated should be pretty easy to achieve. My brother drove my Prius for several short hwy trips back on summer too, all of which delivered at least 50 MPG (calculated) and he drives slightly above the speed limit.

No, I am not idling just to mess with the MPH, that's ridiculous, but if you still don't believe, how about next time I use my Garmin and show you a picture of "moving average"... how dare you...

There are no stops during my way. Off course, a 68 MPH does not mean I drive at 68 steady for all 360 miles, but rather it means, sometimes I cruise at 75 but sometimes slower roads force me to cruise at 65 MPH, and then there are 3-4 intersections that slow me down considerably but do not cause me to stop the car. It is moving all the time.

No.

 

To make a long story short, back in the end of summer, someone mysteriously left my back passenger door open inside my garage and I did not noticed it when I pulled back... the door hit the garage frame and forced open... no damage to the car but the door.... so, the repair shop decided to go ahead and replace the whole door and the insurance company agreed. Some of my best tank MPG were obtained after the door was replaced, so don't even consider that as a possible factor...

No, different dealer. The one that said that is the one I bought the car in Indy, but I service my car in WI.

 

Attached are 2 more charts with sample pooling after 26 hwy trips.

First: MPH vs. MPG

Second: Air temperature vs. MPG... PS: Where it reads ?20 should be <20 F

The influence of temperature is a lot more clear as the data up to date suggests...

UPADTE: Charts now are correct! I replaced only the TEMP vs. MPG chart... the MPH vs. MPG chart was correct. Interpretation is unchanged.

 

I only run the heater when my wife complains she is cold in the car. Most of the time it is off. I also run the defroster (front and back) only minimally when needed.

Unless there is something really wrong with my car, I think the major problem are the hills. Going up a hill drains the gas tank and it takes miles of downhill to make up for one short up hill.

 

Yesterday, I saw a high temperature of 18 F. My total travel distance was 47.1 miles. Speed was a mix, varying from some slow city driving to 10 miles at 70 MPH with a lot of suburb. The end result was a displayed average of 49.6 MPG.

That chart is a calculated summary.

Please provide the raw input data for it.
.

 

Thanks, there is indeed a mistake in the charts... will fix it later. Sorry.

 

No way are you losing more than 10MPG going from 32F to 20F - no way. Something else - probably aerodynamic - is wrong. If you're seeing a "bump" in efficiency plotted against mph, then it's probably your tires - vibrations "resonating" at certain speeds and being less efficient.

As for expecting 50 MPG lifetime, that was unrealistic. EPA highway is 48. 48!!! And that is using the EPA test pattern, not doing 75mph. Realistic would be 45mpg lifetime at that speed (year-round avg). I have never gotten the EPA highway mileage from other cars unless I did 60mph.

 

The charts are incorrect... sorry, I'm fixing them!

Regarding my expectations... We already beat this to death but my lifetime MPG for my Odyssey does deliver at least 3 MPG above EPA and my lifetime for previous CR-V delivered at least 5 above EPA... and that is redardless of winter, driving at high speeds, heater on, A/C on, etc... see, that's what I expect for a decent car!

But, if you insist with the exact EPA number... remember... while my data shows hwy only data, my lifetime reflects about 15% city and 85% hwy, so let's say I should expect 49 according to EPA, in that case, my Prius is unlikely to deliver that lifetime MPG! Right now my lifetime is at 46.8 but I belive it will reach lower 40's by the end of winter and there will be no time to rebound in the summer according to some of my calculations... but we will have to wait to confirm that.

 

So we'll rule it out. I thought that would get your attention and focus on the seriousness of the issue.

Something is not right with your car. When the warm weather returns, you may not get the 58 MPG again. Do you want to wait until then to confirm? You seem to be convinced that ONLY the cold weather is to be blamed and excused any other possibility. I am not here to deny the data you are collecting, just here to help you figure out the irregularly low MPG from your car.

 

I am not surprised with 10 Hondas under your belt. You only have your Prius for what? a couple of months and do you think the car is broken in? Are you broken out of driving Honda non-hybrid habits?

I get 5+ MPG above EPA in the summer and 2 MPG above in the winter. Majority of my miles are on the highway HOV lane.

 

I just corrected the charts on post # 466.

 

That is the ideal, to wait for 1 whole year cycle... and I'm willing to do that because that works fine since my Audi dealer said it will be a lot easier to find my trade if I can wait until July-Aug...

Who knows... maybe I will be surprised in July and not trade it at all... but somehow I just think that will be unlikely... I have other issues with my prius... it is not "just" the less than expected FE.

 

Indy,

How about rent another Prius and see if it produces the same "low" MPG?

 

Already checked that... I could not find a 2010 Prius here in IN or in WI to rent... besides, my wife did not like the idea at all... she is already mad because she thought trading the CR-V for the Prius back on June was a very bad idea... I talked her into it by showing that it financially made sense because of the gas savings with my new upcoming trips. I changed from 10 miles/day to 100miles/day, so the trade was supposed to make sense, but she was probably right, again … I do miss my CR-V…

 

Just picked up my 2010 Prius III and said goodbye to my 2005 Prius.

In the midwest the temperatures dropped into the teens (and lower) recently. No doubt the demands of keeping the cabin at 72 degrees and maintaining proper engine operating temperature has impacted my mileage. It doesn't bother me in the least. I know that when temps warm up I'll be back in the sweet spot.

The reason I bought a Prius wasn't so much for the mileage. It was because I believe we have to support a new way of making cars. The hybrid is a fantastic move in that direction. I will never buy a traditional gas vehicle again.

I understand the disappointment of finding out that cold weather, wind, rain, and road type impact mileage. I remember that first sting of realization too. I guess it is a fact that I'm happy to live with for now, knowing that hybrids and all electrics will improve in the future.

Thanks to Toyota and others I'm looking forward to driving an all electric vehicle when I'm ready to trade in my 2010.

 

Good for you but I just don’t think like that… at least now and in the immediate future.

There are many ways to conserve the environment other than buying a gas-electric hybrid, which comes with many compromises IMHO... but I already made my point about it... no need to keep beating this dead horse :deadhorse:

Congrats for your new car...

 

I have 4K miles and my mpg went from 45 mpg to 28. Yikes! I have begun to do the math and frankly, it is worse than that - 23mpg. And I have been using eco mode as I am a stop ad go city driver.

Any hints? The dealer said no top a block heater and I am skeptical of the grille blocks. I would like any help or suggestions as this was supposed to be my "dream car". It is our third Prius. We had a one and two generation - no problems, now this. Any hints?