Why would you want a higher electric only speed in a non-plug in hybrid?

 

Yes. I was being overly simple.
The FEH is complicated.



And to Tuna... Higher EV speed would only be an advantage for persons who went only a few miles per day, but used those miles on the highway.
You're right to assume that a kWh is a kWh and the advantage to MPG does not matter of you use it at 20 MPH or 70 MPH.

If you ONLY ( or mostly ) drove at high speeds, then you may not use up all the available charge in a PHEV in "hybrid" mode, which is gas+electric.

Does that make sense?
In other words, in EV mode, the battery is doing all the work.
In Hybrid mode ( above 40 MPH ) the battery is only doing some of the work.
In a PHEV the battery contributes more at highway speed than the current model we have does, so a PHEV is still advantagous to the highway driver.

I used a PHEV FEH for a weekend.
I got 90 MPG on a 60 MPH highway cruise, and 141.5 MPG in the city.
The reason the city wasn't Infinate MPG is, the torque of the FEH does not change, so when you press the accelerator, the gas engine kicks on at the same point it does now. However, a program change give you assist all the time, not just when you floor it, so I got better than 141 MPG.

HTH,
-John