For the most part, that's because the benefits aren't shown up in EPA testing. But a few automakers are also worried that customers may not be accepting of the gas-saving technology.
Chevrolet needn't have worried with the Malibu, which utilizes stop-start on the base 196-horsepower 2.5-liter engine.
According to Wards Auto, the media and customers alike have reacted positively to the technology. It could encourage Chevy, like Ford and its recent desire to apply start-stop to many of its vehicles, to spread the tech across other models in its range.
Stop-start was introduced as one of several detail changes to the 2014 Malibu over the 2013 model. It features a new nose and more interior space, as well as the gas-saving system.
Chevy says it offers many of the benefits of a mild hybrid system without having to drag a heavy battery around--though the Malibu with stop-start does feature a second 12v battery in the rear, powering accessories while the engine is off.
In fact, it's enough that Chevy has killed off the Malibu Eco mild hybrid--since the 2.5-liter Malibu with stop-start achieves the same 25 mpg city, 36 highway and 29 combined as the hybrid did, but pricing is several thousand dollars cheaper.
The main benefit of offering stop-start on the base Malibu is that a wider range of customers will benefit--arguably doing more to save gas than offering a much more expensive hybrid that fewer will buy in the first place.
It also gives Chevy a jump over competitors, brand marketing manager John Hahn told Wards--since Chevy offers it on "a mainstream engine that has been purchased by 90% of our buyers", while other automakers tend to offer it on top-end models, such as Mazda with its i-ELOOP Mazda6.
The tech could eventually expand to models like the Impala. In addition, Chevy intends to further extend its use of natural gas dual-fuel vehicles--and a CNG Malibu could be on the way.
By making gas-saving technologies available on mainstream models, Chevy is making real strides towards improving the fuel efficiency of its range.