Electric power is only one part of the Chevrolet Volt equation.

While it's a part that covers two thirds of all Volt miles driven, the other third is handled by its range-extending 1.4-liter Ecotec gasoline engine.

The 2016 Chevrolet Volt is expected to downsize to a three-cylinder unit to boost efficiency, but few other details are known--apart from perhaps its power output.

General Motors has announced the latest round of investment for a new engine lineup, and among the details are news 1.0 to 1.5-liter, three and four-cylinder engines, with power outputs starting at 75 horsepower.

Unless GM plans on dropping a 1.0-liter, three-cylinder, 75-hp engine in the Chevrolet Spark (and there's a chance, in other markets at least), it seems likely the lower-power unit is destined for use as the Volt's range-extender.

ALSO READ: 2016 Chevrolet Volt To Launch Next Year: What We Know So Far

The current 1.4-liter produces 84 horsepower, helping charge the battery and in rare cases, assisting the electric motor directly under high-load situations--steep hills at full throttle, for example.

If GM's figures do indeed reference the Volt's new range-extender, it's a little less powerful than before, but the main aim is fuel-efficiency.

At the moment, the 2015 Chevy Volt has a gas-only mileage rating of 37 mpg combined (35 mpg city, 40 mpg highway).

That's not bad, but does mean Volt owners regularly requiring the range-extender's assistance aren't achieving particularly high gas mileage--a regular hybrid such as Toyota's Prius might be better in such scenarios.

MORE: 2016 Chevrolet Volt To Debut At Detroit Show, First Teaser Photo Released

A new three-cylinder engine would likely be lighter than the current 1.4-liter four, have reduced internal friction and as a result, use less gas when called into play.

GM is investing $233 million in its Spring Hill manufacturing complex to produce a range of small gasoline engines between 1.0 and 1.5 liters and three- and four-cylinders. Power ranges from 75-hp to 165-hp, with a mix of naturally-aspirated and turbocharged units.

Spring Hill already manufactures GM's 2.0-liter turbocharged direct-injection engine, as well as 2.4 and 2.5-liter direct injected Ecotec units.

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