I have my doubts on that type of series hybrid ever being successful. I saw a presentation that walked through the energy flow of that system. The gas engine is only being used to recharge the batteries, not drive the wheels. So after the 40 miles of driving from the fully charged battery, that gas engine needs to generate a lot of electricity to maintain a normal speed vehicle. Many have speculated that the gas engine that GM is using cannot manage a normal driving speed after 40 miles. It would likely be in "limp" mode because that size gas engine cannot generate enough electricity to propel the weight of the Volt. When the GM Volt is actually in the hands of independent reviews and car magazines, the weakness of the design will become obvious. Toyota is going the right way with their plug-in design. Just my opinion.