have only had my Hybrid a few months now, so mostly summer driving.
There is grocery store that is 1.5 miles from house - trip there is slightly uphill the entire way, so trip back is mostly downhill. Usually when I make the trip back, I can get EV mode of at least .9 out of 1.5 miles.
Over the weekend, I made the trip with Temp = 55 degrees. Even though a fairly moderate temp, I got 0 EV mode. I had cabin temp set at 72. Did ICE stay on for cabin heater? Engine was in "Ready" state.

 

Interesting observation... I was driving around last night to Ambient Air Temperature was in the low 60 and I noticed I didn't get that much mileage on EV mode neither. Didn't have AC on or anything just the seat warmer set on lowest setting I doubt that would cause any major differences.

Waiting do hear from other sports hybrid drivers especially RLX hybrid guy. He seem to have the most experience with these ICE motors. We just got ours only a few weeks as well.

 

Did you have cabin temp set and on Auto? Seat warmer will come on with heater operation unless you manually turned the warmer on.

 

No. I manually turn on Seat Warmer.

 

so virtually same conditions this evening on same round trip. 54 degrees. Cabin temp 72
.7 mile EV

 

My guess is that it's emissions related. Cooler ambient means a longer time to heat the ICE to optimum temperature for minimum emissions. Just like the Non-Hybrid models use a different transmission map to hold upshifts off until higher rpms when cold.

 

When we switched over to the winter blend gas and the heat was being used primarily, I noticed the same degradation of mpg in both hybrids. My typical mpg in the RLX Sport Hybrid now is back into the 26-29 range as the heat is in use which is related to the ICE engine operation, thus less EV only use. The EV mode still kicks in when coasting most of the time, and at stop lights the ICE shuts down. However if I am sitting for longer than a few minutes with the heat on, the ICE engine kicks back in quicker than when the heat is not turned on. This is the same experience in the MDX Sport Hybrid and that has pulled back to 26-28 mpg on average now.

 

my 130 mile trip that I normally get 30/31 dropped to 26 yesterday. Temp was 48