Mazda’s innovative and award-winning SKYACTIV suite of technologies continues to expand, this time in the 2014 Mazda6. Powered by a 2.5 liter SkyACTIVE-G gasoline engine, this fun and sophisticated mid-size sedan now features an available i-ELOOP regenerative braking system that adds to the car’s impressive fuel efficiency, boosting its official EPA ratings to an estimated 40 mpg on the highway and 28 mpg in the city, for a combined 32 mpg.

Those are pretty good numbers for non-hybrid small cars, but exceptional for a conventionally-powered mid-size model. This efficiency enables up to 650 miles on a single tank of gas. If you drive the average 15,000 miles each year, that means your visits to a gas station could be limited to every two weeks or so, depending on your driving habits.

Mazda’s i-ELOOP – for Intelligent Energy Loop –is not a hybrid system since recovered braking energy is not used for acceleration assist or electric-only operation. It’s also different because, unlike other regen systems that store recouped electrical energy in batteries, i-ELOOP uses a supercapacitor. The system’s double-layer capacitor can be discharged and recharged many more times than batteries with far less deterioration and will likely last the life of the car.

When a driver lifts off the accelerator pedal, i-ELOOP recovers kinetic energy as the vehicle decelerates. A variable voltage alternator generates electricity up to 25 volts for maximum efficiency before sending it to the supercapacitor. A DC/DC converter steps down the supercapacitor’s output from 25 volts to 12 volts for use in the car’s exterior lighting, climate control, audio system, and other electrical components. This reduces the need for a normal engine-driven alternator to generate the electricity required to run these systems, a real benefit since a conventional belt-driven alternator’s parasitic load on an engine decreases fuel efficiency.

In urban driving with frequent acceleration and deceleration, i-ELOOP can provide nearly all of the electricity these systems require. Headlamps and other exterior lighting, heating/air conditioning, wipers, and the audio system account for about a 40 amp draw, within the capabilities of the DC/DC converter’s maximum throughput of 50 amps. On a cold day, particularly right after starting, it’s possible the defogger and optional seat heaters may exceed the DC/DC converter’s capacity, in which case the electrical system reverts to conventional alternator-powered operation and bypasses the capacitor system completely.

At times when available e-ILOOP-generated electricity exceeds the electrical load, electrical energy charges the car’s 12 volt battery. When no regenerative braking energy is available, the alternator charges the battery but now through the DC/DC converter. Battery capacity is unchanged since it must still start a cold engine when the supercapacitor is not charged.

Supercapacitors accept and release charge very rapidly and only store electricity temporarily, so they must be topped off before each stop. However, it takes just a few seconds to fully charge the capacitor. The Mazda unit can accept a full charge in just 8 to 10 seconds. Although it can discharge in as quickly as 40 seconds, discharge may take up to 113 seconds at minimum load.

Mounted beneath the hood, the cylindrical supercapacitor is 13.8 inches tall, 4.72 inches in diameter, and weighs just 13.2 pounds, with its required heavier wiring harness weighing in at 3.3 pounds. Mazda says that the e-ILOOP system brings an approximate 5 percent fuel efficiency improvement under real-world driving conditions, which contributes to the Mazda6 achieving its best-in-class EPA fuel economy rating.

The i-ELOOP system in the Mazda6 is part of an available GT Technology Package that also includes Mazda radar cruise control with forward obstruction warning, lane departure warning, high beam control, and active grille shutters. All this extra goodness comes at a cost of $2,080, bringing additional SKYACTIV technology to the road that helps deliver impressive fuel efficiency while attending to the performance and fun-to-drive nature expected of the brand. Want to know more? Watch the video here.

There’s more to come. Soon, the 2014 Mazda6 will also offer a 2.2 liter SkyACTIVE-D clean diesel engine, Mazda’s first diesel in the North American market. Plus, the Mazda i-Stop stop/start system that’s available in markets outside the U.S. is in the pipeline for the States. Mazda reportedly will introduce this system here in the Mazda6  in 2016.