I wonder how much some of the newer vehicles that turn off when at a dead stop help improve mileage. Even at idle, a car uses fuel. Saving that two minutes of gas has to make a difference. It's very interesting to see how they just stop the engine still under compression to reduce wear on the starter/battery. I'm still not sure it's a great idea, but it should help with mileage. We test drove one by Toyota, but passed on it for other reasons.
I never realized that Otto cycle was replaced by the Atkinson cycle in a lot of hybrids. It's still amazing that 140 years later, we still have the same two basic types of ICE.