Until now, the 2014 Mazda6 was EPA rated at up to 38 mpg on the highway, but Mazda’s optional regenerative braking system – which is now available on North American-spec Mazda6 models – effectively bumps that rating to 40 mpg.
Mazda’s regenerative system, called i-ELOOP, is largely hinged on a freewheeling, variable-output alternator. During deceleration, the alternator engages in a typical fashion, charging the system. The alternator – which can produce between 12 and 25 volts -- then charges a double-layer capacitor, which is able to quickly absorb and store pulses of electricity. The so-called capacitor’s output is then fed through a DC-DC converter, which knocks the voltage back down to 12 in order to both charge the vehicle’s battery and power the car’s electrical system.
Step on the throttle, however, and the alternator freewheels, leaving both the capacitor and the battery to power the car’s electrical system. This reduces the load placed on the engine and subsequently improves its fuel economy. With the exception of the supercapacitor, i-ELOOP is very similar to BMW’s EfficientDynamics brake-based energy recovery system used across that automaker’s lineup.
According to Mazda, 2014 Mazda6 sedans fitted with the i-ELOOP system retain the same 184-hp, 2.5-liter direct-injection four-cylinder engine, but are EPA rated at 26/38/30 mpg (city/ highway/combined) when paired with a six-speed automatic transmission. Add i-ELOOP to the mixture, and the 2014 Mazda6 is rated at 28 mpg on the city test cycle, 40 mpg on the highway cycle, and 32 mpg combined.
There’s one catch: i-ELOOP is only available on the Mazda6’s top-tier trim grade, and only as part of an optional equipment package. That means you’ll need to pony up $30,490 (including $790 in destination fees) for a 2014 Mazda6 Grand Touring sedan and then fork over another $2080 for the new GT Technology package, which lumps i-ELOOP with lane departure warning, adaptive cruise control, forward obstruction warnings, and automatic-dimming headlamps.