From the beginning, inviting the Silverado Hybrid into our long-term-test fleet was a roll of the dice. In 2003, the word "hybrid" was just beginning to take shape--it was simply understood as the blending of two technologies or designs. Three short years later, hybrid has come to mean something more specific: a combination of electric and gasoline motors working in tandem to offer significantly better fuel economy, lower emissions, and an environmentally friendly persona, all with relatively invisible (to the driver) technology. This particular definition left our long-term Silverado Hybrid somewhat misnamed, as many of our drivers noted when the vehicle didn't deliver on the expected hybrid promise. To begin, some tech explanation is necessary.

The Silverado Hybrid system uses a 14-kilowatt integrated flywheel starter-generator, replacing the alternator and traditional starter to take over shutoff, startup, and charging duties. The system allows the engine to turn off when running downhill, coasting, or braking to a stop, saving fuel and limiting emissions. Releasing your foot from the brake or touching the throttle will restart the engine. Unlike in other hybrids (Toyota, Honda, Ford), the Silverado's 42-volt battery system (stored underneath the extended cab's rear seats) supplies little power assist to the driveline while accelerating (it applies torque to smooth early converter lockup); however, it can convert its power into four (two in the cab and two in the bed) 110-volt, 20-amp outlets, able to run power tools, lighting fixtures, appliances, and anything else with a plug. Power comes from the same 5.3-liter V-8 offered in other half-ton Silverados, so the Hybrid can tow or carry anything a regular 5.3-liter pickup can. But as good as it sounds on paper, the Silverado Hybrid's daily-driving characteristics presented a few problems.

Logbook comments during the Hybrid's 15,000-mile run questioned the value of the $2500 hybrid-system option for a mere 1.0- to 1.5-mpg benefit. In real-world driving, the best improvements, not surprisingly, came during heavy stop-and-go traffic (here on L.A. freeways)--the Silverado averaged 15.5 mpg. Certainly not stellar when compared with EPA ratings of 17 city and 19 highway, but our long-term 2004 4x4 5.4-liter V-8 F-150 averaged 12.8 mpg (MT, February 2006).

The Silverado Hybrid was serviced once at 8700 miles, after its information display panel indicated less than 10-percent oil life remaining. Perhaps GM buyers love to keep track of every volt, degree, and remaining percentage of fluid life; depending on how deeply one wants to scroll, the information display features reams of such details. A recurring low-oil-pressure light came on intermittently, even though all fluid levels measured within the appropriate parameters. A complete diagnostic found no problems. The light never came on again. The service center replaced the weather seal around the passenger-side door panel to fix a worsening wind noise. A loose brake pad further made a funny sound during hard stops. Total price for repairs: $41.76, and we were on our way.