2015 Chevrolet Impala Adds Stop/Start, Drops Hybrid

The 2015 Chevrolet Impala enters the new model year with two changes to its powertrain lineup. The base 196-hp, 2.5-liter inline-four engine receives a stop/start function as standard, while the optional mild-hybrid eAssist powertrain has been discontinued.

Adding the stop/start feature as standard means the four-cylinder 2015 Chevrolet Impala returns 1 mpg more in the city, now boasting fuel economy of 22/31 mpg (city/highway). Chevrolet says that engineers carefully tuned the car's engine mounts to reduce shudder when the engine restarts, fitted a heavy-duty starter motor, and designed an algorithm that requires the car travels at 6 mph between engine shutdowns, preventing frequent starts and stops in heavy traffic. For 2014, Chevrolet added a stop/start feature to the Malibu sedan.

At the same time, the 2015 Chevrolet Impala will drop its optional eAssist mild-hybrid system. Previously, the eAssist powertrain returned 25/35 mpg thanks to its combination of a 2.4-liter inline-four gas engine and a 15 hp electric motor. A Chevrolet spokesman said the powertrain had been discontinued because it was chosen by fewer than one percent of Impala customers, and attributed that low take rate in part due to the eAssist powertrain's higher cost. However, he said that in general GM will continue to explore using eAssist or other hybrid technologies in future vehicles. The 2014 Chevrolet Malibu also ditched its eAssist option last year.

The 2015 Chevrolet Impala's 3.6-liter V-6 engine is unchanged, with 305 hp and fuel economy ratings of 19/29 mpg. Pricing for the base model starts at $27,735 including destination, while the V-6 version starts at $30,960.

The real reason the eAssist only had a 1% penetration was that it did not save much fuel.  My last rental Malibu eAssist (a 2014 model with a lower curb weight than the Impala) struggled to make 30 mpg even when hitting the 'reset' button on level Indiana freeway.  That is 6 mpg below the EPA highway number!  That is what happens when you design the car for the EPA cycle rather than the real world - and the end result are unhappy customers.  So the Impala lost 5 cu ft of trunk space for nil real world performance improvement.  
I have regularly exceeded the EPA highway number in rental Altima's, Camry's, and even a 200.  In the case of the Altima, I saw 39 mpg at a sustained 70+ mpg on a 2000 mile trip that included cold temps and lots of 2 lane mountain highway passing (NM, CO, and UT).

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