Why Mileage Gets Worse in the Winter

I have 2004 prius with 300k+ and it went from50mpg to40 in one week any ideas no mil light

 

Are you a new owner of this vehicle? If so, that's probably winter drop due to different fuel mix, colder temps, etc. If you have owned this car for more than one summer->winter transition and this drop is unusual, then at 14 years old and the mileage, I would say start thinking about the traction battery.

 

I've had car for 5 yrs no trouble runs fine battery gauge shows battery cgarging fine runs fine in all electric up to about 25mph then engine kicks in no pinging air filter new spark plugs new oil new tires new only time it did this before air filter clogged

 

FYI
A couple of thoughts and suggestions

First on Gen2 and many vehicles ambient temperatures has a noticeable impact on miles per gallon and fuel consumption... winter will for sure drop mpg

to mitigate some fuel pump pain
purchase a SG2 from autozone
winterize vehicle
purchase oem block insert heater and oil pan heater
plan your trips for warmest part of day


I am currently getting around 52- 53 mpg on my gen2 prius however ambient temps are going to drop so I am more than expect a drop in that current reading

 

Is it normal to have two squares, in gas tank dash display to drop upon travelling only 40 or 50 miles?

 

Maybe more so with second gen with the variable of the internal bladder in the gas tank? My guess would be a touchy gas station pump that shut off sooner than usual.

 

I'm getting better mileage in the mild winter of South Texas. The hotter than hell 'window' of 6 months in our Summer strains the battery. The ICE is turning more often

 

Did you buy normal tires or thr LRR tires? I have read that the low-rolling-resistance tires actually start with worse fuel economy until they get broken in.

 

That sounds like a tire salesman brush-off tactic.

 

I don't sell tires, that suggestion was made to me by an established member of this forum.

 

Sorry, I'm not saying you do, just that it sounds like it might have originated with a tire salesman.

Also, "low rolling resistance" is a very loosely defined term in North America, with no official testing: manufacturers tend to put that tag on a broad range of tires, some a lot better than others.

 

The normal line in this forum is that such applies to all tires, not specifically to LRR tires.

 

funny that this forum is the first and only place I've ever read it

 

This link will explain tire break in.

https://www.discounttire.com/learn/breaking-in-new-tires

 

I live in southern Missouri and we have constant temperature changes throughout the winter months. Some days are sub 32* while the next few days might be above 60*. While driving during the cold temps. I've noticed that the fuel mileage in my gen2 prius is around the high thirties. When the temps. are over the mid fifties then the mileage raises to the lower 40's. The changes in fuel mileage is NOT due to a wonky A/F ratio sensor or a plugged air intake, but rather to …..cold temperatures. One day the temp could be 12*F and my fuel economy will be 38 mpg even when babying the throttle. The very next day the temperatures could raise to 60*F and I can hammer the throttle and my FE will jump to mid 40's. Then the next day back to 32*F and the FE drops to high 30's. Nothing on the car has changed, in fact the only change is the ambient air temperature.

So the air temperature is the main culprit to poor FE in the winter time. Now for kicks and grins, come back in the middle of summer when the temps jump to 100*F and see how the FE jumps. I bet your Prius would be hitting close to 45+mpg during those temps.

Prii seem to love hot temps and hate cold temps. Just my two cents.

 

yep, once a/c weather arrives, my mpg's start dropping again

 

Battery performance in colder weather does have a more dramatic effect than running the a/c in 100 F on mpg
I can drive up into the mountains and drain my warm battery, park over night at 32 F upon starting the car the ICE (internal Combusion Engine) runs at 1500 RPM until the battery is over half full and the cab has reached it’s 72 F set point.
The point I’m making is that the car will get the best mileage if I drive it while it’s warming up.


iPhone ?

 

Couple of thoughts... I live in western NY State so winters can be cold. The ICE is not a very large engine so on very cold days it probably can cool off pretty quickly. A cool gas engine means it needs a richer air/fuel mixture. And of course it needs to run more to keep the heater warm. Hence poorer gas mileage. Winter gas is blended differently leading to poorer mileage. Cold weather lowers the pressure in your tires and that contributes to lower mileage too. I also run snow tires in the winter which are softer rubber which has higher rolling resistance. Again, impacting mileage. Of course, the amount of ethanol in gas (boy ethanol is a dumb idea) will also impact mileage.

 

This is helpful. I neglected to consider this in reviewing my mileage.

 

I haven't experienced as big of a difference as the others here with the drop in MPG, but that being said.. it's most likely the fuel