First Drive Review
This is GM's self-proclaimed "no-excuses hybrid." You can have it all: a gargantuan SUV with seating for eight, a big 6.0-liter V-8, towing, hauling, four-wheel drive, and fuel economy. That's right, GM's first "full" hybrid boosts the four-wheel-drive Chevrolet Tahoe/GMC Yukon's fuel economy by a whopping 43 percent on the EPA city cycle and five percent on the highway cycle to a V-6 Toyota Camry-shaming 20-mpg city rating, as well as a 20-mpg highway rating (21 city and 22 highway on two-wheel-drive models).
As part of this "no excuses" business, GM is proud that, unlike some single-purpose hybrids (think two-seater Honda Insight), the Tahoe maintains all existing functionality and features. Mark this one down: The Tahoe is the first hybrid to come with keyless starting; heck, it's even standard. That's right, Mr. and Mrs. Overindulgent American Greenie, the press of a button fires up six liters of gas-guzzling V-8 goodness in the driveway. You may be worried about your carbon footprint, but a cold leather seat is no way to start the morning.
What, you thought Toyota would think of this first?
Impressive Mechanicals
Making this fuel-economy leap possible is a host of changes, but the most interesting is GM's patented two-mode hybrid transmission that packages in the same space as one of the company's venerable four-speed automatics. What sets this system apart from the popular Toyota hybrid arrangement is that the Tahoe can run as a continuously variable transmission (CVT) and an automatic through one of four fixed gear ratios. With their theoretically infinite ratios, CVTs are much better than conventional automatics at keeping engines spinning at the most efficient speeds, but at constant highway speed, that advantage can be nullified by the internal friction inherent to CVT operation. In hybrids, the energy loss can be even worse because the drivetrain must also spin an electric motor. The Tahoe, however, can switch over to a more-energy-efficient mechanical path (one of the fixed ratios in the automatic) to minimize wasted energy whenever possible. Whereas the Prius is always processing its power through the CVT, even at inefficient highway speeds, the Tahoe's system is better and can simply bypass the electric motors and lock onto a gear.
