ICE on more frequently

2011 Prius Two 25k miles

Been seeing a slight MPG reduction. I could easily assign it to all the winter factors (fuel, friction etc..) But didn't see this reduction last winter.

One thing that has occurred is I can see the ICE is on more frequently. In particular, there is a well traveled road that I can usually go a few miles in electric mode keep the power demand below the midway on the ECO meter. Now the ICE will come on even if battery is fully charged and I limit the request for power. I also experience the ICE coming on going down a particular long hill where it has never come on before. Battery also nearly fully charged in this case too.

We keep our cabin temp at 70 degrees with fan on 1 bar like we have the entire time we've owned the car.

Anyone experienced this?

 

My driving pattern hadn't changed much. Very much cued to the ECO gauge for fuel economy. But this is my wife's car and she is the main driver.

Climate control is on manual. Defrost always on and fan on 1 bar. We've had it that way forever due to the wet climate here in Northwest. Seems like this isn't a new change.

I used Techstream (Toyota diag tool) to look at the battery parameters (attached). My car was on but just parked so ICE is not on. All looks fine. There are 3 temperatures readings on the battery with one (Temp of batt TB2) higher than the other 2 but all seems to be within reasonable range. Wonder how other people's Prius hybrid system reads.

 

Its hard to measure because my wife is more of a lead foot than I so ICE is on more often for her anyway. She also gets probably a couple of mpg less than I in a more aggressive driving style. The last 1500 miles are mostly her driving pattern and I'd say we went from 50.x to 49.x so about 1 mpg drop (we live in a hilly region). Nothing major but just surprised the ICE on frequency changed when I drive on a common route near the house.

I'll try some kind of reset next to see if I can get rid of any bad learned habits.

 

yes, I'm less concerned about mpg and it is very difficult to get the difference without a longer term observation. I only said 1mpg based on a short term observation. It could be 2-3 for all I know.

I'm mainly wonder why the ICE on frequency is changed on a well traveled road when I'm driving the exact same pattern. Again, the patterns are

- Going down a long hill, battery is nearly all charged (only 1 bar is unlit). At the bottom of the hill while coasting, ICE comes on for whatever reason with no power demand (foot not on gas). I've read the ICE will come on to prevent damage to battery and drain the excess charges. But the car has never done this before even with all the bars lit up cruising down this particular hill.

- Driving along a flat suburban road at 35mph with most of the battery bars lit. Power demand is 1/3 on the ECO gauge. I've been able to go a couple of miles like this previously without ICE. Now ICE would randomly fireup in this condition.

I'll try to drive this road with Techstream hooked up and see if I can see what interesting parameters change when ICE fires up.