You're probably right about the Insight II steady state FE numbers (smaller car, smaller engine, better SS FE), but you're wrong about the EPA test. The real reason the raw numbers are so high is that EPA tests are conducted at low speeds, where the Prius drive train is most effective. Once it gets warm (and I think the test starts with a warm engine?) the engine shuts down any time power isn't needed below 40-45mph (depending on if we're talking 2nd or 3rd generation.) That's an awful lot of ICE-off driving in the city cycle in situations where it would still be turning in an IMA-type hybrid. One thing you have to understand is that HSD is set up not to deplete the battery by using it for propulsion except in extremely slow stop & crawl. I start and end every journey with SoC within a percent or two of 60%. The farther below that level the battery gets, the harder the system works to get it back up through greater use of the ICE and less use of electric motor. The opposite true the higher SoC is above 60%. This strategy ensures that there is room to capture regen energy or provide assist or a short run of low-speed crawling, whichever is needed. What was this thread about? A capacitor-based BAS-type system? I'm happy to see it come to market, especially when coupled to Mazda's excellent new engines. Chemical batteries do get the job done, but I think it will be hard to get around the need to treat them with extreme care in order to make them last the life of the vehicle. Heat degrades them, cold makes them not work, too much current degrades them (and makes them hot), too much or too little charge can cause degradation while they aren't even being used...fussy stuff. Capacitors have their own issues, but in this application I think they make a huge amount of sense.