Colder weather has zapped my mileage to 44mpg

I just filled up and only got 42.6 actual; computer says I got 46.7. I was getting about 47 until now with the comp claiming 48-49. Temps in the SF Bay Area have dropped sharply; much of my driving on this tank, which was early morning or late night, was done with temps in the 30's. My last car, a Honda Civic HX, suffered a 10% drop in mpg under these conditions; looks like the Prius does a bit worse. I picked up my car Nov. 2; I'm hoping my summertime mpg improves as much as my wintertime mpg has dropped
As for the displayed mpg, does anyone know if that factors in starting the car or only driving it? If the gas used for a really cold start isn't included that could explain why the discrepancy has gotten bigger.
Oh and my heater is working just fine. Outside temps are in the high 30's. This car warms up a bit faster that the old Civic did.

 

It's all included, stand still warming up, heater use, driving and any others.

Ken@Japan

 

Huh, I'll have to fill up once again in this cold. Maybe some of what I'm seeing is just differences in when the gas pump shuts off but this is my fourth tank and the first three were very similar as far as mpg. This last one really took a dive and diverged considerably from computed mpg.

 

This evening was the snowy commute, where the roads were covered with the white stuff and it was still coming down pretty heavy.

Top speed was 50 MPH. As soon as I crossed the river, I stopped for gas and reset the trip meter. I had 13.5 miles of slow driving to look forward to, fascinated by what the 2010 could reveal. The discovery process is quite exciting.

Anywho, I watched speed, efficiency, and temperature.

Outside, it was 21°F. On the highway at 65 MPH, the normal operating temps waver between 190°F and 195°F. Going much slower, often with the engine off, I knew it would be lower. Between 141°F and 163°F was what I observed. That worked fine for keeping me comfortable and kept the engine from running longer than I had experience with the previous generation. Near the end of my drive, there's a mile-long hill you climb at 45 MPH. The coolant temp quickly shot up to 190°F. That fired up the heater from comfortable to hot. That was impressive... and a good clue about preventing heat loss and grille-blocking effectiveness.

Speed while driving averaged about 30 MPH. There were a few stoplights with extra long waiting. That resulted in the displayed overall average to be 20 MPH.

Efficiency was delightful. Starting with a warmed engine from the gas station, those 13.5 miles of driving resulted in a displayed value of 51.8 MPG.

Winter fuel, tire pressure, heat retention, traffic differences, engine warmup, etc. It's a bummer that the circumstances for excellent MPG are so complicated. Heck, just think of all the unnecessary heat a traditional vehicle creates during the summer that our hybrid tries to avoid.

I don't have any suggestions beyond the usual helping of individuals who post problems & concerns. It's just nice knowing how much awareness we are raising... which will be beneficial in the long run.
.

 

I also think the filling levels are different on each tank.
I would like to suggest to do a math using "moving average" method for three tanks or more.

Ken@Japan

 

Thanks for the info but I can get anything above 50 MPG even in Antarctica if I reset the trip meter after the engine is warm and driving in the speeds you mentioned... not surprised.

 

John,
Very nice results. I don't understand one comment of yours though. Why did the heated cabin air heat up on the hill ? I thought the G3 was like a G2, in hte sense of the operator setting a desired temp. Or are you saying that the cabin temp never reached your chosen temp until the hill ?

 

I know well that a V6 engine delivers faster and warmer hot air... but I used my V6 just as an example... I used to have a 1999 Hyundai Accent that did a lot better than my Prius as far as heating fast and properly the cabin... I'm pretty sure that engine is smaller that the 1.8 ICE in the Prius... so, what would be the explanation in that case???

Oh, BTW my Prius A/C works a lot better than my V6 A/C...

Why? Let me think... because bumping it up makes a heck of ventilation noise, but you know what... it may help masking a little bit the rattle symphony in the dashboard... too bad that, in the hwy, with all the wind/road noise plus the heater vent noise plus the rattles, my ears won't have room for a nice and decent audio book or song...

Here I can't argue with you!

 

There was no desired temp. You get it all when it's set on HI, which is what I was curious about. That worked out great for checking the potential available.
.

 

I have noticed a 3 mpg jump (FEC) after lowering my temp from 74F to 68F. I use a seat heater and plan to lower the cabin temp down to around 64F and see if there is further improvement. Currently, most of my trips tend to be short (5 miles) on city streets. The seat heater gets very warm and is probably enough for me. Outside temps are ranging from 18F to 34F this past week.

 

John got his MPG above 50 because he reset the trip meter after the engine was warmer and he drove at relatively slow speeds compared to me. My trip MPGs are recorded from a cold start until I turn off the car in my destination and I usually drive at 75-77 MPH whenever I can... My dealer said that even with 99% hwy and cold weather the Prius should be able to keep at or near EPA estimates (which is 48 for hwy) and this is not happening at all.

 

He was either clueless or dishonest, because the EPA estimates don't account for speeds that fast or temperatures this cold.

Start your research here... Fuel Economy Test Schedules

.

 

I vote for both...

 

Wow, I must jump in here!

I did not have the same experience with my past cars, which I recorded the mileage. Not at all!

My previous CR-V would get close but always above EPA estimates with city driving and considerably better than EPA with hwy driving during winters, no matter how cold it was, or driving on snow, or cold rain, or heater on all the time, you name it! Same thing for the current Odyssey.

I think the EPA estimates for my CR-V was something like 18-25... That was a joke by EPA! I consistently got 24-25 with city-only driving on it and close or over 30 with hwy driving. So, during winters, I got a drop but, most of the time I still managed to keep considerably above EPA in both cars and we are not talking about the long trips I am doing now with the Prius. My commute used to be very short!

 

75+ mph, winter conditions, 44 mpg.

What part of the obvious are you having trouble understanding ??

 

Prius:75+ mph, summer conditions, 58 mpg. (Indicated)
Prius:75+ mph, winter conditions, 44 mpg. (Indicated... actual is 41)

CR-V: 75+ mph, summer conditions, 30 mpg. (actual MPG)
CR-V: 75+ mph, wnter conditions, 28 mpg. (actual MPG)

Odyssey: 75+ mph, summer conditions, 25 mpg. (actual MPG)
Odyssey: 75+ mph, wnter conditions, 24 mpg. (actual MPG)

Need an explanation?

 

The explanation is that the Prius wastes less energy than the non-hybrids under ideal (EPA) conditions, but loses some of that ability in less than ideal conditions. The non-hybrid, by contrast, is wasting heat energy all the time, so the winter thermal loss is just rounding difference. 41 is still better than 24 or 28 by 71% and 46%. So the 5 passenger 3000 lb+ Prius is 46% better in winter than your 5 passenger CR-V, still offers a lot of cargo room and flexibility, and creature comforts. If the laws of physics applied to the CR-V = 28 mpg, is it that surprising that the Prius only achieves 41 when those same laws are applied to it?

I'm sorry that the clueless, dishonest salesman mislead you about what the EPA #'s mean. I hope you will try blocking the lower grill in winter, if only for a tank or two. I get significant benefits on non-hybrid, and believe your results would surprise you.

 

Yes, please.

Why the assumption it would respond exactly the same way as a traditional vehicle?

It's a hybrid.
.