30 mpg? When they're whining about having to meet something like a 22.5 mpg fleet average?
GM seems perfectly willing to tell its customers that merely by bolting a hybrid drive system to their existing vehicles, they'll somehow achieve amazing mileage numbers. With a little imagination I can just hear their 2008 ads now: ".. and our NEW Yukon Denali hybrid can tow a boat up a mountain, in 4-ft deep snow, while still getting 50mpg!!1"
Umm, no. For a 6,000-lb vehicle with all the aerodynamics of a Vermont dairy barn and a ton of rolling friction, it's just not possible to get that kind of fuel efficiency.
Which is why you've got to give Honda some mega-kudos for doing a complete redesign of the car (aka the Insight) to show how it can be done.