I have also experienced the exact same scenarios when driving. I have often thought that the car had its own personality and was like, "Ok im going to go into EV mode when I feel like it" kind of thing.

Honestly that is what it seems like. These things DO have a mind of their own..dont they???

But the article that Ken showed everyone here does make sense. It seems like when the car has been running for awhile, and when it is warm and it does finally get into that "EV ZONE", it is really, REALLY fuel efficient.