Here in Maryland, we're having a bit of a cooling off period with regards to the summer weather. Temps are averaging in the 80's during the day and in the 60's at night and in the morning.
I've noticed that I'm getting 2-3 more mpg than I had been getting during the summer when it was very hot. Is this normal, and what can I expect during the winter months?
Right now I'm averaging around 51.8 on my tank and during the hot days of summer it was closer to 48 something.
Thanks all, and I hope I can keep the mileage up. I've just become a hypermiler in the database - woohoo!!

Cheers!
ChesapeakeTechie

If you are using the AC this would explain your increased gas mileage. The compressor cycles on less often, therefore requiring less power for a given duration. Lower power requirements means higher mileage.

You can expect seasonal changes to affect your mileage. The summer is bad because of using A/C. The winter is also bad because the Civic won't autostop below 41 degrees (at least, my 03 won't - I'm assuming the 05 runs on the same rules). However, I plan to do a lot more manual shutoffs this winter to compensate. Also, I've found that rain reduces mileage as well (the extra resistance of the water on the road). My best months are Aug-Sept (mild temps so no A/C, and no rain).

*** Retired after 65,000 outstanding miles ***

Ouch. I had no idea. Can anyone verify if this is also true for the '04s? I hope they tinkered with my '05, but if not, at least 41 degrees doesn't come often in FL. Makes up for all these hurricanes.

Cold weather is most definately harder on mileage. You get the best mileage at the hottest temp you can stand without AC. AC lowers mileage but not as much as cold (winter) temps.

This was in my users manual under Auto Idle Stop. The exact condition is ECON button selected and temp is +41 degrees, or fan dial is off. Now, I don't know if that means if the fan dial is off then temp condition doesn't matter, or if the car would accept either ECON button selected or fan off. I know it autostops with the fan off (turning the fan off turns off the ECON button). Will have to wait until winter I guess (although my fan is never off in the winter because the heater is running...).

*** Retired after 65,000 outstanding miles ***

I get the BEST mileage in 70-80 degree weather and low humidity. I think the humidity makes more of a difference than the temperature; lower is better. I live in Baltimore, and the car performs less efficiently when the temperature and humidity are both close to 100 (most PEOPLE don't perform too well under those conditions either, ha ha.)

We had snow Christmas eve and I was working at 6:00am on my way home it was 30f and auto stop worked for me. Let me say that it worked as I pull in the driveway with the heater off.Kevin

2004 silverblue 5 sp.

I guess maybe I'll just turn the heat off well before coming to a stop if my temps get that low.

One bright note to the extreme heat that I've noticed: my tires just fly and so do my MPGs when I'm driving on red hot pavement. I mean the exact same streets and same traffic and same season. My morning drive into work starts at 6:45 AM and though it's already 80 degrees, the blacktop isn't hot at all because the sun isn't up yet and my tires drag. Afternoons out are around 4:00-5:00 usually and the roads would melt skin off your feet. I know it has to immediately add 2-3 PSI to my standing 45#s, which I can always tell in the difference of my instant FE bar.

...in general, almost EVERYTHING is designed to operate optimally around room temp. Computers, machinery, humans, plants, wild animals. Imagine that- built to the average / most common condition.

Beyond AC, air and fuel are a little denser at cooler temps, improving efficiency. Heat rejection is more efficient too. Around room temp everything is set up to be in the Goldilocks state- juuust right. Colder, and the engine has to use energy to stay in the good spot.