The Audi A6 could be seen as a singular kind of sleeper. It sells in volumes that are one-half to one-third those of its German competition. The sedan doesn't command a conversation much less the imagination, its history bereft of iconic brand identifiers. Think of the way the E28 BMW 5 Series turned the segment into something to be proud of, or those double headlamps from the W210 Mercedes-Benz E-Class, or that other E from 1986 simply known as Der Hammer. There is currently no RS6 sedan in the US to draw halo attention to the clan. And it was the first in its segment to slip into a design lassitude such that you had to check the badge to make sure it wasn't a different Audi.

However, I look at the A6 from the other side: it's an underappreciated gem. With the 3.0-liter supercharged V6, it's a thoroughly fun steer. It has more power and torque than the competition. I think it has the finest interior. It's probably my favorite sedan in the segment considering how many boxes it checks before you cross the bridge to things that begin with S, M, and AMG.

But you have to get to know an Audi in order to comprehend what it possesses, and the "product improvement" rolled out for the 2016 A6 won't change that. I'll call these "blind spot updates," because someone needs to point out where they are, and even then you've got to work to see them. Nevertheless, they're there, in places like the wider grille, new headlights and taillights with revised LED DRL signatures, new bumpers, side sills, rockers, and trapezoidal tailpipe finishers.

The interior and driver assistance systems get gussied-up.

The interior and driver assistance systems get gussied-up, too. The base A6 2.0T can be had with driver aids now – Audi pre-sense comes standard, the night vision assistant will identify animals, and the blind spot monitor works with lane keep assist to give you even more warning before changing lanes. There are two new colors and new inlays, like the layered walnut on the tester I drove, which is an upper-tier luxury feature that's finally filtered downstream.

The biggest interior rework comes via the MMI system, which gets the Nvidia Tegra 3 quadcore chip pushing graphics to a retractable, eight-inch touchscreen. The additional processing power allows for new features like expanded codec playback – you can now play uncompressed .flac files straight through the stereo. The proprietary MMI cable is no more, replaced by two USB jacks, one for charging only and one for charging and hooking into the car. Full Google Earth images appear in the dash cluster, as opposed to a compass or just the arrows during turn-by-turn navigation, and can be scrolled independently from the main screen. Map updates will also come over-the-air. You can use your Audi Connect account to navigate from a photo that someone sends – the system reads the geotagged data – and traffic updates come via INRIX, not Sirius anymore. And those are just a few of the improvements and possibilities.

This is a development step called MMI II, beyond what just came out in the Audi A3. The MMI II Evolution coming in the Q7 will be a development step beyond this in the A6. Annoyingly, you've still got to turn the MMI knob to the right to go up, to the left to go down, though.

The 2.0T jumps from 220 horsepower to 252, and from 258 pound-feet of torque to 273.

More interesting is what's under the hood, with the installation of the third-generation 2.0-liter turbocharged four-cylinder. This motor was extensively redesigned, with the exhaust manifold being placed inside the aluminum block, which then necessitated a complex thermal management system that ultimately aided engine efficiency and gas mileage. Even production processes were changed; pre-development engineer Dr. Rainer Wurms said that the shapes of the cylinders in the block change slightly when the cylinder head is attached, which the piston rings are engineered to account for. With this third-gen engine, the cylinders are bored while the block is under the simulated stress of the cylinder head. When the actual head is attached later in production, you not only get the round bores you drilled, you get another tiny improvement in fuel economy.

The 2.0T gets new features like a variable valve lift system, a dual fuel-injection system, an electric wastegate on the turbo, and low-friction oil. The result is a jump from 220 horsepower to 252, and from 258 pound-feet of torque to 273. Efficiency improves from 20 miles per gallon city and 29 mpg highway to 22 city and 32 highway with Quattro all-wheel drive. Audi also ditches the old CVT for a dual-clutch transmission on front-wheel-drive models, which now offer economy numbers of 24/35 mpg city/highway.

The supercharged 3.0L V6 now has 333 hp, up from 310.

Buyers of the 3.0-liter supercharged engine haven't been left out of the upgrades. The power improvement there takes the six-cylinder engine from 310 hp to 333, while torque remains the same at 325 lb-ft. One of its new features is an electric clutch on the supercharger that disengages the forced induction when not needed. The upshot is better gas mileage, going from 18 city and 27 highway to 20 city and 30 highway.

Audi will continue to offer the A6 with a 3.0-liter TDI engine, as well. The torque-happy V6 is still good for 240 hp and 428 lb-ft, achieving fuel economy numbers of 25 mpg city and 38 mpg highway. It's no slouch, too – hitting 60 mph in the 4,277-pound TDI takes just 5.5 seconds.

A day behind the wheel of the 2.0-liter A6 shows it is plenty of car. We Americans like all of our numbers to go up, including – or perhaps especially – displacement. But consider this: The 1986 Audi 5000 CS Turbo Quattro made 158 hp and 166 lb-ft from a 2.2-liter five-cylinder engine, got 20 mpg on the highway when fitted with the three-speed automatic (24 mpg with the five-speed manual), was a lot slower than this 2.0T A6 even though it weighed 600 pounds less, and it was one of Car and Driver's 10Best Cars that year. It also cost $28,000 new, at a time when a 3.2-liter Porsche 911 Carrera could be had for $32,000.

The A6 is markedly improved everywhere, in ways that go beyond its facelift nips and tucks.

What a difference 30 years makes. The little 2.0-liter four-cylinder has plenty of power for its mission, and it's quiet until you push it high up into the rev range. In fact, the cabin is quieter overall because of double-pane front windows that are now standard fitment. I think it's impossible to complain about a midsize luxury sedan with a little four-banger that gets from 0-60 miles per hour in 5.8 seconds and gets good fuel economy, when the 2010 Audi S6 needed 5.1 seconds for the feat and it had a thirsty 5.2-liter V10 underhood. Also, fun fact: The A6 2.0T Quattro is nearly a full second quicker than the front-wheel-drive model, which takes 6.7 seconds to hit 60 mph.

The transmission is a sizable part of that equation. Engineers haven't had to lean hard on the gearbox to improve fuel economy, so the eight-speed Tiptronic is free to serve up the right gear for the driving you want to do. It doesn't bog your acceleration trying to get up to the high ratios as quickly as possible. It doesn't hunt around for cogs, and it isn't afraid to downshift. During a couple of hours in the canyons, it held the correct lower gear to keep the revs up as I turned in, and every horse was ready to run when I hit the corner apex and the throttle. It never did me wrong. The 40 percent of A6 buyers putting money down on the 2.0-liter are most likely not looking for sedan this sporty, but it's in there if they want it.

Since this is a mid-cycle refresh, it isn't really fair to pick on the overwhelming subtlety of its design and complain about the fact that we don't see the promised Audi Prologue Concept influences yet. The unsubtle achievement here is that the base-model A6 experience – which starts at $47,125, including $925 for destination – is markedly improved everywhere, in ways that go beyond its facelift nips and tucks.