Why do the miles per gallon go down in cold weather? I have a HCH 04. I go to the casinos in Indiana twice a week. During the summer and warm weather the 67mile trip from Cincinnati would usually show a mpg reading from 57 to 59 round trip. The last two trips were taken with the temp in the low 50s and the mpg has been 51 and 54. Much of the running is just ICE with no boost so battery temp should not come in to play,,,,,,,,,,or does it? Is it the same with the Prius?
Thanks

 

There are several causes:
1- the ICE has to run more to keep the engine and catalytic warm
2- There is more rolling friction at low temperature (affects all cars)
3- Wet weather causes additional rolling resistance.

Yes cold weather affects the Prius as well. My 2004 has 43k miles and averages 46+ but gets about 40 in the winter (CT) and better than 50 in the summer.

 

I asked that question a few days ago at How Much of an FE Hit Does Cold Weather Make?

 

Im really glad you brought this up. My brand new PII went from 55mpg to about 45 because of this cold front comming through chicago. I was actually going to take it back to the dealer and have them put the scope on it. It seems that the engine runs alot more and i cant use true EV as much because even a gentile touch on the gas starts the engine up. any other prius owners experiencing this ?? thanks . Dean

 

Dean, Looks like you and I are in the same boat... It just got cold a few days ago, and I had a really hard time getting my MPG to stay from dropping like Bush's approval rating. While its only 60ish... My tank that was enjoying life at 61.2 is now chilling at 58.4 and my driving has not changed much... I have read a post or two from people who made some modifications to help this problem. I might have to revisit those posts.

 

I'm morbidly interested to see what my HCH's first winter does to its FE. Of course, when I say winter, I'm one of the lucky ones here that doesn't really get a winter.