When General Motors sells Saturn later this year it will lose more than a quarter of its sales of hybrid vehicles. Saturn, with no V8 models, full-size SUVs or pickups, is GM’s most fuel-efficient brand and is second only to Chevrolet for overall hybrid sales with its Vue and Aura mild-hybrid models. One of these models, the Vue crossover, was destined to spawn an advanced plug-in hybrid variant, however, now this model will be sold under the Buick brand.

Set to arrive in 2011, the new Buick plug-in hybrid will be able to seat five adults and is expected to be the first commercially available plug-in hybrid crossover produced by a major automaker. A standard version powered by a range of direct-injected gasoline engines, however, will be available from next year.

As this teaser image reveals, the new crossover’s design (especially the headlights) will be very similar to the outgoing Saturn Vue. According to GM, it has the potential to achieve double the fuel economy of comparably-sized SUVs and crossovers on short trips. This is because of the significant boost in economy achieved by combining a modified version of the automaker's 2-Mode Hybrid system with lithium-ion battery cells and charging technology developed for the Voltec system, which will debut in the Chevrolet Volt plug-in hybrid late next year.

In fact, the Buick plug-in hybrid will use the same manganese-spinel based chemistry and polymer battery cells as the Volt. The 8 kwh battery - containing half the energy of the Volt battery pack - will be packaged in a rectangular-shaped box under the cargo floor. The lithium-ion battery can be fully recharged in four to five hours by simply connecting the vehicle to any standard 110V household electrical outlet. In early testing, the plug-in hybrid is capable of electric-only propulsion for more than 10 miles at low speeds.

On the road, GM's 2-Mode plug-in hybrid system can use any combination of electric or gasoline engine power to move the vehicle, depending on the driving conditions. Importantly, this differs from GM's Voltec technology, which provides the Volt with up to 40 miles of emissions and gasoline-free electric-only propulsion, and an overall range of more than 300 miles when using its internal combustion engine.

In addition to the lithium-ion battery pack, the Buick plug-in hybrid's powertrain features two powerful electric motors, sophisticated electronic controls and battery management systems and an efficient direct-injected 3.6-liter V-6 flex-fuel capable engine.

As for the non-hybrid versions, they will be powered by either an Ecotec 2.4-liter direct-injected four-cylinder engine or a 3.0-liter direct-injected V-6. Final fuel economy estimates, as well as additional vehicle details such as name and pricing, will be announced in the near future.