According to my TCH tank mileage display, my mpg has dropped from a rock-solid 38 since May to about 30 for over a week now.

I've added tire pressure to compensate for temp loss.
I've also read about oil companies changing their blend for the season.

I've always used Shell's 87 octane -- would moving up to 89 help?

I suspect that this is also the result of reduced driving.
My daily commute is less than 10 miles in town.
Is the outside temp sensor running the ICE to keep me warm?

Here's a link to an online article that seems to verify that a Toyota heat recovery system AND an electric-only mode is possible:
http://www.treehugger.com/files/2006...id_minivan.php


Any replies will be appreciated.

 

I was up at 37 overall since June, but my last tank was calculated at just under 34 (display showed 36). My current tank is displaying 28.8, which could turn out to be 26! I, too, have a short commute, 6 miles each way. Normally, though, I have one trip per tank of 50 miles each way and that tends to give me an MPG boost. This tank so far has been ONLY short trips--nothing over 10 miles. So, once I go on my "long" trip this weekend, I'm hoping to bring that number up some.

Clearly, short trips and cold weather really hurt. My previous car got 22-23 in the middle of winter on the same commute. So, it's still better.

The bad mileage also coincided with my first (and only so far) oil change. I sure hope the dealer didn't use 10w-30 dino oil! Of course, there's no easy way to know....

 

The last few tanks for me have been dissapointing as well. I typically get around 40 MPG, but the last couple tanks have been during rain/ice weather with temperatures between 25 and 45. The displayed averages have been around 38 and 39 MPG, which translates to around 36.5 to 37.5 MPG. I know it is not as big a hit as you have been taking, but my typical commute is 60 miles one way.