08kermit — The quote in your second-to-last paragraph is both relevant and correct. One could make a regular automobile more fuel efficient under steady-state driving conditions (constant speed on a flat road) by having an assortment of "super-overdrive" gear ratios available to "lug" its ICE. This would force the ICE to run at a more efficient operating point at the power level required at that speed. The trouble is that a big (read "powerful") ICE is not very efficient at the low powers required for such steady-state driving. Far better is to make a smaller (read "less powerful") but more efficient ICE, like an Atkinson/Miller-cycle engine, and use the two electric motors to regulate the speed at which the ICE runs so as to achieve highly efficient, low-rpm ICE operation under these conditions. That's precisely what a Toyota/Ford-type full hybrid design does! Indeed, at high speeds in "heretical mode" the ICE is being lugged in precisely this way by MG1 (the "generator") using electrical power coming from MG2 (the "traction motor"). The ECVT gives the designers the option to do things like this that aren't feasible in normal vehicles. The even more complicated (and expensive) two-mode hybrid systems now appearing have an even greater capability to control the ICE's rpm over the vehicle's full speed range, and to tow significant loads too.

Stan