Last 2 tanks have dipped just below 30mpg US. Almost all trips have been 15min trips in temps around -15C to -10C (5F to 15F) so the car is pretty much constantly in warm up mode. It was pretty rare that the engine would ever shut off, but recently I noticed the heater was not in ECO mode. I've had that back on for the last 3 or 4 days and the engine will now shutdown a bit more often at red lights even when it's not fully warmed up.

I've pretty much had the same drop in my Sienna too, about 25% down in this really cold weather.

 

Yup, my last two full gas tanks were 37 and 34 MPG, which is waaaay below than my 40+ MPG in the warm days.

 

I wonder why such a significant drop in mileage for the TCH? I'm just using my Civic as an example. This winter my mileage has only dropped by 1.5 to 2 MPG. It's not uncommon for me to drive to work with temps in the teens. We do have single digit temps occasionally. My trip to work is about 12 miles and consists of highway and city driving...I think in our CRV we've lost only 1 MPG. Hmmm...

 

My commute is only 5 miles. Temps have been sub-zero for the last 7-8 days with -18f being the coldest so far. The ICE runs continously - even when on a much longer drive. My instant MPG is showing 25 right now and I had 1 trip that was 100 miles highway where the instant MPG was showing as high as 34.

Keeping the cabin warm is one reason the ICE runs a lot. There are at least a couple of other reasons I can attribute poor FE to;

1) The AIr Temp is very cold - the o2 sensor will indicate Stoich to the ECU which in turn richens the fuel mixture to accomodate the more dense air.

2) In MN we have "Oxygenated Fuel" which means there is roughly 10% ethanol automatically blended into our winter grade of fuel. There is less BTU of heat in alcohol per given volume than compared with gasoline.

3) Longer warm-up periods for the ICE to come off it's cold start fuel mixture program.

4) Rolling resistance through snow / slush - while we have had very little snow so far this winter - any snow will cause a decrease in FE.

Well - that's it from somewhat sub-tropical Minneapolis MN.

 

The ethanol really nails me in Colorado - been avg 30 -32 in the winter - last fall I was 36-38 when it was warmer and no mixed fuel.....

 

I'm in Kansas and my current tank average is 31.5, my last was 29. I miss the warmer weather!!!

 

I have been in the mid to low 20's lately...chicago area with below zero temps....I dont think about it,,,,better days are ahead with warmer weather

 

Temperatures in NJ have been around 15-32 F in the last couple of weeks.
My commute is 6 miles each way, I average 26 mpg when only commuting, but this gets much better (tank average = 32-33 mpg when I go to ski, aprox 60 miles each way, once a weekend)

 

same here in Boston, most days are short trips and it's a struggle to get up to 30 mpg - took a long trip to NYC and got 33-34 (same trip in the fall was 39)

 

Mine is 31-35. Been tracking it but haven't entered it into the database yet.
I warm up the car for 5 minutes or so, so that hurts economy as well.