I know the theory is that the batteries get some recharging from the electric motor acting as a generator when the car decelerates by braking or when coasting downhill, but it doesn't seem to me that the relatively small amount of time that process is taking place compared to the much longer time that the storage batteries would be discharging energy instead of receiving it would make the savings from the recovered energy almost inconsequential.
As you can see, I am no mechanical or electrical engineer, but I think I do have a basic understanding of the principles of conservation of energy. It takes a certain amount of energy to overcome the combined resistance to movement of the tires, wind drag, and weight of the car whether that energy comes directly to the wheels from a gasoline engine or from a battery pack which stores and discharges energy to the wheels, energy it receives from the gas engine by the charging process. Where is the energy saving other than the relatively minuscule amount that is recovered through braking. Am I missing something?
2.2 gallons to again top off the tank after driving 136 miles, mostly highway, up and down hills, some stop and go traffic. I can't really explain it...it just works the way it is expected to.
They get their greatest mileage gains in the city where the engine is shutoff at stop and the battry store is used to power the electric engine from light to light, depending on the hybrid in use.
Highway mileage is also improved but by a much smaller amount.