2014 Mazda6: i-ELOOP, There It Is

Waste not. Want much.


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With a thriftiness that could only come from growing up during the 1930s, my father has always preferred to save his brakes by coasting to stoplights and taking curves far too fast. In theory, it's a good idea: Brakes convert your car's forward momentum (good!) into heat (bad!), and not using them will save you money—at least until you rear-end another car or careen off a cliff.

Saving brakes by not using them follows the same logic as putting a slipcover on a couch, or patches on the elbows of a blazer. That's why Dad should drive a Mazda6 Grand Touring with the Technology Package, which features a unique regenerative braking setup. It's inexplicably called i-ELOOP, and though it's price tag won't please cheapskates, it has a certain appeal for those who hate waste.

But first, some background

Instead of converting kinetic energy to heat, regenerative brakes recover that energy and store it. It's either used to power accessories or to give the car extra oomph during acceleration, and ideally cars with regenerative brakes get better fuel economy than their traditional counterparts.


The capacitor sits beneath the front right corner of the engine, behind the wheel well.

There's only one problem: Weight. Traditionally, hybrid vehicles have sent energy recovered by regenerative brakes back to big, heavy batteries. Mazda's decided to go a different tack, adding a capacitor instead of a battery as an energy-storage device.

Capacitors can't hold energy as long as batteries, but they're great at rapidly charging and discharging. And Mazda's capacitor design is lighter than a battery, so you won't waste fuel hauling around a fuel-saving device. It's a brilliant and elegant way to save a few mpgs—a Mazda6 equipped with i-ELOOP is EPA rated at an astounding 40 mpg highway, 28 mpg city, while a conventional Mazda6 gets a still-respectable 38 highway, 26 city.

Does it work?

I got the chance to drive an i-ELOOP-equipped Mazda6 for a week, and almost duplicated the same routes I took in the conventional 6 I drove about a month earlier. As expected, i-ELOOP improved fuel economy by about two miles per gallon. I got 29.2 with i-ELOOP, 27.5 without.

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Outside, there's no hint of the capacitor within.

Unexpectedly, the i-ELOOP 6 is virtually indistinguishable from the conventional sedan. About the only physical difference I could find was an additional screen hidden inside a menu on the gauge cluster. Select it, and it'll show energy flow to and from the capacitor. There's no special "Eco" badging, and the word "i-ELOOP" thankfully doesn't appear on the outside of the car.

I was most impressed that the Mazda's regenerative brake setup didn't feel any different when coming to a stop. Drive a Prius or any other conventional hybrid, and you'll instantly notice an uneven grabbiness to the brakes that takes some getting used to. Coast, and the i-ELOOP-equipped 6 will offer a hint of what feels like engine braking. Otherwise, it's no different from the standard sedan.

It'll cost ya

If the fuel savings appeal to your inner Scrooge, the price of entry won't. You can only get i-ELOOP on the range-topping Grand Touring trip as part of the technology package. For that, you get a fully-loaded car with lane-departure warning, automatic anti-collision braking, radar cruise control and active grille shutters that make the car even more aerodynamic. Total MSRP is $32,845. Compare that to an identical i-ELOOP-less car, and you're spending an additional $1355.


An i-ELOOP display screen is one of many choices for the gauge cluster. It's the only hint of what lies under the hood.

Based on EPA estimates, you'd have to own the car for more than ten years before the fuel savings equals the cost of the option. Since regenerative brakes don't get as hot as their conventional counterparts, that payback period may come down a bit if you don't have to get your brake pads replaced as often—a benefit that Prius owners have reported.

None of that would matter to my father, however. He'd rest easy at night knowing that the Law of Conservation of Energy suddenly works in his favor, returning energy that would've been lost to braking to power his car.

I'm inclined to agree. Though cheapskates may balk at the Mazda6's initial purchase price, the car itself is one elegantly engineered tightwad.

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