In the ’60s, General Motors explored alternative power sources with a number of experimental vehicles, including this one: the XP-883 gasoline/electric hybrid.

The term hybrid has been employed to describe countless automotive configurations over the years, but here we mean hybrid in the most recent sense: a vehicle with two power sources, internal-combustion and electric, that can be used separately or together to propel the vehicle. This hybrid concept as we know it didn’t originate in the ’60s or with General Motors, of course. Early examples include the 1916 Woods Dual Power, while Ferdinand Porsche developed a series hybrid with electric hub motors in 1898, the Lohner-Porsche.

In response to growing environmental concerns, GM was actively experimenting with nearly every kind of alternative power in the late ’60s, including steam, Stirling engines, battery electric, and fuel-cell electric (See our features on the Electrovair here and the Electrovan here). The car shown here was one of two gas/electric hybrids the automaker was working on at the time. The other, the ES-512 Hybrid, was smaller than a golf cart and featured a 12 cubic-inch engine. The XP-883, shown here, was more of a serious automobile with 2+2 coupe bodywork and a weight of 2100 lbs.

The see-through drawing above reveals the XP-883’s mechanical layout. Both the gasoline engine and the electric motor are mounted up front and drive the front wheels. The DC series-wound motor was mounted co-axially with the front half-shafts and drove through a 5:1 planetary gearset and differential. Meanwhile, the water-cooled 574cc opposed-twin gasoline engine (small enough to escape emissions regulations of the time) was positioned ahead of the electric motor, coupled to the drive unit via a worm gear. Independent rear suspension allowed the six 12-volt lead-acid batteries, charged by the engine’s flywheel alternator, to be mounted low under the floor.

A parallel hybrid, the XP-883 ran on electric power alone up to 10 mph, when the electronic controller started up the piston engine. Under acceleration, both power sources were engaged, while at steady cruising speeds the gas engine alone provided the propulsion. Zero-to-40 mph came in 14 seconds, while the 60 mph top speed arrived in 28 seconds. The forward-mounted controller included an onboard inverter so the battery pack could also be charged at home with a standard 120-volt extension cord, so the XP-883 qualifies as a PHEV in the current lingo.

The example shown here, sporting a fiberglass coupe body with Vega-ish styling and a rear-facing passenger seat, was described in the GM literature of the time as a mock-up. The show glider was displayed at a number of venues, including the 1974 Spokane World’s Fair, below. (The car also makes an appearance in the 1969 GM presentation Progress of Power you can watch here.) However, the volume of available info on the project, including performance data, points to at least one running and driving test mule as well. GM introduced its first hybrid production vehicle, the Saturn Vue Green Line, in 2007.