It's happened already. After one or two sub-freezing nights, not only did I lose the best tomato garden I have ever had but my 2005 is exhibiting the dreaded cold weather driving behavior that drives me mad. It's like somone flipped a switch and now it is a regular ICE vehicle.

I drove around base all day yesterday watching the mpg go from around 40 (full tank) to around 32 to 30 when I hit the interstate for the 100 mile drive home. I stayed at 60-65 for the ride home and was at least able to get up to around 35.8 but the last 7 miles or so are back roads with lots of stop signs and the ICE never shut off until I pulled into the driveway. It is maddening since there is no charging going on and the vehicle is obviously warm.

I've come to expect this as normal behavior in cool/cold weather but it drives me crazy since it is so different than when it is warmer out and much different than the '06. Time to switch back to the '06.

Just venting I guess.

 

Check the air pressure in your tires. It drops in cold weather and this increases rolling resistance. It won't completely restore MPG, but it helps to keep the PSI near the rating on the tire sidewall (never above).

JeffD

 

Since you aren't a regular on this part of the site, let me tell you a little about me.....

A couple weeks ago I went on vacation in a rented minivan. The first thing I did after getting the car (well, after resetting all the trip computers) was to check the tires and inflate the crap out of them. They were 5.5 pounds below the door tag recommended pressure. I went two over the tag.

Anyway, I keep my tires at 40 psi and knowing we had some cold weather coming, I went a few pounds over normal (max is 44 in these tires).

For some reason, my '05 is much more cold weather sensitive than the '06. It drives me nuts.

I appreciate the advice though.

 

Ray,

There are other factors as well that cause our hybrid MPG to be affected more by low temperatures. The main one is the need to keep the ICE, catalytic, and you warm (to satisfy the EPA). This causes the ICE to run more in cold weather (and prolongs the warmup cycle).

I'm curious why the difference between your 05 and 06 FEHs. Do you have different tires? If so the tire rubber compound may have different rolling resistance at low temperature. My Michelin MXV4+ (LRR rated) tires get noticably better MPG in cold weather than my OEM Goodyear Integrity tires and in warm weather they were about equivalent.

JeffD

 

Like I said in the original post, after driving 93 miles on the interstate, I'm pretty sure everything was up to normal operating temperature, the battery was fully charged and it should have gone into EV as soon as I stopped the first time. This is a common occurence in my '05 in cool weather that no matter what, it won't go EV. I make this exact trip every month and in the warmer weather the last 7 miles I am running EV most of it in either FEH. In the cool/cold weather I am mainly EV in the '06. In the '05 it stays on. The '06 does better overall by far in cold weather than the '05. In warm weather I think they are about equal. If I didn't have the '06 I never would have known that the behavior is strange. The dealer says that unless I have a trouble code, there is nothing they will do to it.

One of lifes mysteries that I have been trying to solve since I bought the '06 and realized how differently it behaves. The two cars are practically identical. The '06 has side airbags. The '05 has the appearance package. Otherwise, identical except for color. Tires are the same. I drive them the same way.

So, I guess my plan from here is drive the '05 in the warm months and the '06 during the cold months. My wife does maybe 200-300 miles a month so the difference with her will be trivial. I do 1500 or more a month.

 

Ray,

I would check if there's a firmware update for the 05 that you can get the dealer to flash for you. My 2004 Prius has been updated via recalls three times so far (none were MPG related).

JeffD

 

Great idea that has been bouncing around this forum for a while. I can't get my dealer to even look at it unless it is actually exhibiting some problem. Not performing like my other car is not, to them, a problem. A check engine light, error message, or some other failure would get them to act.

https://www.greenhybrid.com/discuss/...ight=reprogram

https://www.greenhybrid.com/discuss/...hlight=reflash

Maybe I just need to go into the dealership and use the tried and true method to get the service department to get their heads out of their tailpipes - cash. It's sometimes amazing what can get done when you drop a 20, 50 or 100 dollar bill on someone. Wouldn't be the first time I have paid baksheesh to get what I want. It's much more acceptable than threats of violence that used to work so well - getting too old for that now.

 

Ray

Try shifting to "N" and tapping the brake pedal under 40mph to go EV. When it gets cold here, I notice the battery does not like a full charge and will not allow regen at its higer SoC. If you are in "D" or "L", tapping the brake maybe interupting EV mode with regen. The only thing that would be cold after a trip like that is the battery because there is no heater for it. I think from what I've heard you post in the past, the '06 has been programmed to handle regen better with lower RPM run-up's in "L".

GaryG

 

Ray,

I found this suggestion on Edmunds:

One other thing are they both 2WD, 4WD or different?

JeffD

 

*IF* they are firmware compatible... nothing says there isn't a difference in the hardware between the 05 and 06 that makes them incompatible... a sensor here, a different calibration for a sensor there and you have a car that doesn't run or runs like crap. You should be able to flash back to the old flash if that were to occur, you can on a computer... but not always.

We've already seen they changed the cabin air intake on the '07's. They tend to make little changes every year if it can save them a dime.

Thats part of the reason why the dealer doesn't want to do it unless he is told to by Ford.