Chevrolet's Volt plug-in hybrid won't be arriving in showrooms for at least another two years, but a careful eye may spot one of the many development mules testing its hybrid powertrain on public roads.

Our spies did just that, snapping some pictures of the Malibu-bodied test vehicle as GM engineers took it for a spin outside of the automaker's proving grounds. Although the vehicle's body is radically different from the slippery shape the production car will wear, we're told the mechanicals beneath the skin are all Volt-specific and stem not from the Malibu, but from the next-generation Delta small-car platform.

That means we're expecting a small-displacement gasoline motor (possibly a three- or four-cylinder) underhood, partnered with electric drive motors. We'd also expect the car to sport some form of a lithium-ion battery pack, as both Continental and A123 Systems - GM's partners in developing the Volt's batteries - have reportedly delivered prototype packs to GM engineers.

Those batteries are reportedly a large headache in pushing the Volt into production. GM hopes to begin mass production of the car in 2010, but development delays threaten to push that date back by nearly two years. When Volts do arrive in showrooms, the added costs of the lithium-ion batteries may push its price tag to $40,000 - nearly $10,000 more than GM originally suggested.

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