The 2008 Chevrolet Tahoe Hybrid delivers 30-percent better overall fuel efficiency than a conventionally powered Tahoe with a smaller V-8 engine. Chevy says the hybrid gets 50-percent better in-city fuel economy than a conventional Tahoe, which translates to a 21 mpg in-city rating. For perspective, keep in mind that’s the same mpg rating a four-cylinder Toyota Camry gets in urban driving conditions.
It’s virtually impossible to tell a conventional Tahoe from a hybrid model by external appearances. From the driver’s seat, the Tahoe Hybrid behaves in traffic and on the open road exactly as a gasoline-powered model would. The SUV comfortably seats up to eight adults, and both the second- and third-row seats fold down to provide ample, secure cargo capacity. All the usual bells and whistles, from heated front- and second-row seats, power windows and mirrors to the premium Bose stereo with Onstar and real-time GPS navigation system are offered as well.
A combination of forward-thinking technologies
GM was able to achieve such impressive in-city fuel economy for the Tahoe Hybrid by bringing a couple of pertinent technologies together on the truck and integrating them seamlessly together.
As with GM earlier hybrid systems, the computer shuts the engine down once its rpms drop into idle range. The actual power transition is transparent: An astute driver will note the engine oil pressure gauge dropping to zero, and the tachometer dropping below 1,000 rpms into a new “Auto Stop” zone. At this point, the Tahoe is essentially a big golf cart running on electric power captured when the SUV is braking or coasting in normal driving conditions.
As long as you keep the tachometer below 1,000 rpms and vehicle speed under 20 mph or so, the Tahoe moves quietly along just fine on electric power. It’s an outstanding system in traffic congestion, on neighborhood streets, parking lots and fast food drive-through lanes. Inside the truck, all traditional and essential vehicle systems function normally: The heat and air continue blowing, power steering works normally, as do the navigation and entertainment systems. The SUV emits zero emissions and burns no fuel when operating in this mode. When it’s time to go, simply step on the accelerator and the computer will instantly re-start the gasoline engine.
The Tahoe Hybrid comes standard with GM’s Active Fuel Management. This is essentially a
computer-controlled engine displacement system. The Tahoe’s onboard computer compares multiple variables such as engine rpm, accelerator inputs and vehicle speed and determines if the engine needs to be running on all eight cylinders or if can get by on four. A read-out in front of the driver lets you know how many cylinders are in use – a helpful tool because the actual engagement and disengagement of the cylinders is virtually impossible to detect from inside the vehicle.
It’s a pretty slick system. And it’s a good feeling to check the mileage readout and see that you’re logging 43 mpg at 70 mph in a vehicle as large as a Chevy Tahoe. Still, it’s worth noting that the Hybrid Two Mode power system works best and delivers its greatest benefits in city driving conditions. The Tahoe Hybrid’s highway mileage is exactly the same as a conventional Tahoe equipped with Active Fuel Management, simply because its electric drive system has no influence on high-speed road performance.
