New information on updates for 2015 to the Chevrolet Impala full-size sedan range note that a start-stop system will be fitted to the four-cylinder model as standard equipment.
So the 2015 Chevy Impala LS model with the base 196-horsepower 2.5-liter four-cylinder will now switch off its engine when the car is stopped, turning it back on as the driver begins to lift a foot off the brake pedal.
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Chevrolet says the four-cylinder model accounts for about one-third of total Impala sales; its estimated EPA ratings are 25 mpg combined (22 mpg city, 31 mpg highway).
2015 Chevrolet Impala Bi-Fuel Natural Gas
The 2014 Impala Eco model, however, which used GM's mild-hybrid system (known in Buicks as eAssist) has been discontinued.
It had much higher fuel-economy ratings: 29 mpg combined (25 mpg city, 35 mpg highway).
According to Chevrolet's Chad Lyons, less than 1 percent of the 2014 Impalas were ordered with the Eco feature.
Chevrolet sold 156,797 Impalas during 2013, some of them the previous-generation model, and has delivered 50,773 of the latest version through April 30.
Using the 1-percent figure provided by Lyons, that means that fewer than 2,000 of the 2014 Chevrolet Impala Eco model have been built and sold to date.
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This removes the last hybrid from the Chevrolet lineup; the 2014 Malibu range lost the Eco hybrid version with which it launched in 2013.
That doesn't mean the GM mild-hybrid system is falling out of favor, however.
2013 Chevrolet Malibu Eco
"We will continue to offer eAssist technology on other products and are committed to this technology," Lyons said.
Indeed, in November 2012, GM's then-product chief Mary Barra said the company would focus on plug-in and electric vehicles over the coming years, as well as continuing with the eAssist mild-hybrid system.
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"We’re continuing to work on the next generation of eAssist for future applications, but we don’t have any specific announcements at this time."
The 2015 Chevrolet Impala LT model comes with a 303-hp 3.6-liter V-6 engine. All Impalas come with six-speed automatic transmissions.
The four-cylinder 2015 Impala LS starts at $27,735 (including a mandatory $825 destination fee), with the six-cylinder 2015 Impala LT at $30,960.
The 2015 Chevy Impala is also offered in a bi-fuel version that uses compressed natural gas, starting at $38,210.