The new Audi Q7 will shed more than 700 pounds.

Among the estimated 45 world debuts scheduled for the upcoming Detroit Auto Show, expect a big one from Audi – quite literally, as it plans to reveal the replacement for the biggest, and oldest, model in its line-up.

The Q7 SUV has undergone only the most modest of tweaks since its original debut back in 2006, an unusually lengthy wait considering the ever-faster pace of today’s auto industry.

Audi apparently intends to address some of the key complaints about the Q7, which include its unimpressive fuel economy, as well as its poor space utilization. Among other things, the big ute will drop more than 700 pounds of mass. It will, meanwhile, get a new plug-in hybrid system which Audi claims will deliver as much as 138 mpg.

The new Q7 will get a plug-in powertrain delivering up to 138 mpg in the European test cycle.

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“The new Audi Q7 is a statement of our competence,” proclaims Ulrich Hackenberg, the Audi Board Member for Technical Development. “Weighing 325 kilograms (716.5 lb) less, it sets the benchmark in its class. It is around 26% more efficient and is equipped with the latest assistance systems, infotainment modules and connect features.”

So-called “lightweighting” has become a major push in the auto industry, and for good reason considering that mass equals mileage. But trimming more than 700 pounds is a significant achievement – about the same as Ford has cut from the biggest versions of its new 2015 F-150.

Audi is using more aluminum on the 2015 Q7, as well as ultra-high-strength and other specialty steels. But the new model is, for all practical purposes, about the same size as the outgoing SUV.

As is the norm for European makers, the Q7 will offer a wide range of powertrains, depending upon the market. In the U.S., the 3.0-liter TDI gets 32 more ponies, at 240 horsepower, with torque jumping from 406 to 443 pound-feet, cutting a full second off its 0 to 60 launch, at 6.3 seconds.

High-tech touches will include a new 12-inch virtual instrument cluster and pop-up infotainment screen.

Even so, fuel economy climbs to about 41 mpg. That’s using the European test cycle, however, and the American numbers will almost certain drop by as much as 25%.

On the gas side, there’s a supercharged 3.0-liter package that gains a whopping 53 hp and 30 lb-ft, at 333-hp and 295 lb-ft in the 2015 package.

Then there’s the plug-in Q7 e-Tron, which will pair a 258-hp V-6 TDI with a 94-kilowatt electric motor to come up with 373 horsepower and a stump-pulling 516 lb-ft of torque.

Again, using the Euro tests, Audi claims 138.4 mpg. Realistically, it might come in somewhere between 70 and 80 mpg using the EPA test process, if other plug-ins serve as an example. Even then, the other impressive stat is a 0 to 60 launch time of just 6.1 seconds – on electric power alone, and 6.1 seconds in the gas/electric mode.

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Quattro all-wheel-drive will be the norm, as will a new 8-speed automatic gearbox. The new Q7 will join other Audi models with new torque vectoring capabilities. The Quattro system can shift up to a peak 85% of torque to the rear axle, or 70% up front. But it also can increase power to the outer wheels to help steer, or vector, through a corner.

Audi says the new Q7 will now boast the longest cabin in its class, with room for an optional 3rd row.

The exterior of the new Q7 is a bit more crisp, with more distinctive shoulders, the overall look picking up on some of the new design cues Audi revealed at the recent L.A. Auto Show in the form of the Prologue concept vehicle. Mounting the mirrors on the body, rather than the window, improves aerodynamics – and reduces cabin noise, as well, according to Audi.

While the new Q7 is about 1.5 inches shorter and 0.6 inches narrower than the outgoing model, the interior is a bit larger, with more space between rows and improved headroom. The maker claims the 015 model will now have the longest cabin in the segment. That makes room for an optional, two-person rear seating package.

The overall feel of the cabin is more high-tech, with fewer buttons and an upgraded infotainment system – with a pop-out screen. There’s also a 12-inch virtual instrument panel replacing traditional gauges. There are also plenty of tech features, including Park Assist and Active Cruise Control with Traffic Jam Assistant.

Audi plans to have the first of the 2015 Q7s in showrooms by next summer. It will announce prices by spring when it begins taking orders.

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