Chevrolet Makes Stop-Start Standard in Base 2015 Impala

General Motors Co.'s Chevrolet unit will equip the standard 2.5-liter 4-cylinder engines in all 2015 Impala sedans with an automatic stop-start system. The car's optional 3.6-liter V-6 engine won't get the technology.

The system will improve the Impala's U.S. city fuel economy rating about 5%, or 1 mpg, according to the company. The first-generation version introduced late last year in the Chevrolet Malibu helped boost that car's city fuel economy 14%.

Stop-start technology is still rare in the U.S. But Navigant Research has forecast that annual global sales of cars equipped with such systems will surge to more than 55 million in 2022 from less than 9 million last year.

GM's software engineers tweaked control algorithms for the Impala's system to minimize engine shudder and cope with "change-of-mind" events, in which the driver begins to stop but then accelerates. Under the latter condition, the technology is designed to engage the starter even if the engine hasn't fully shut off.

Software updates also prevent the stop-start system from engaging until the car surpasses 6 mph after its previous restart. The adjustment eliminates repeated stop-starts under low-speed bumper-to-bumper driving conditions.

In addition, the system continually monitors battery charge, cabin temperature and humidity and other factors to determine whether the stop-start system should be activated at all.

The 2015 Impala, which is base-priced at $27,700, will go on sale this summer.