A few days ago I was driving the usual 8 miles to town. I noticed at 45 mph the car kept going into the stealth mode. The TCH ran a mile or so then went back to the ice only for 15 seconds (to cool) then MG1? kicked in with the ice and ran most of the way to town. I tried to follow it's pattern. I noticed after a couple miles in the stealth mode, MG1 would drop off and maybe cool for 15 or so seconds then is would come back on again. This rarely happens on on the way to town.

I was getting over 65+ mpg at the time and the battery was charged to about 90% which is rare. The trip to town is a slight upgrade at maybe 1%.

On the way home I usually drive at 40 mph so the TCH can run in the EV mode. This time I let the engine run as long as I was getting 75+ mpg at 45 mph. It's very slightly downhill the first half of the way home. I got to thinking to check the outside temperature again. It was 77 degrees on the way to town and 75 on the way back home.

My guess it's either the MG1 temp that needs to cool after helping propel the car for a ways. It could be something related to the traction batteries being cooler. It looks like when it's 75 to 77 degrees is prime time for some good gas mileage with your TCH. (the AC was off)

Once I got home I checked my weather station for that evenings history. I noticed it was rather dry on the way to town but the humidity had came up a lot on our way home. The higher humidity did not seem to bother the cars high mpg performance on the drive, either direction.

Could be that's why during the Spring time and Fall weather is when I usually get my best gas mileage.