Sleepers as a concept are a sinister, yet entertaining way to view sports cars. These types of sporty, unassuming cars give the appearance of regular traffic with restrained exterior designs, but pack a serious punch underneath. Whether it be a powerful engine, sophisticated suspension, or a combination of performance upgrades, sleepers will always have a place in the hearts of many automotive enthusiasts. It just takes a dive into the go-pedal to find out what some of the world's best sleepers can really achieve. Sleepers are a reminder not to take things too seriously.

Often a love letter from the engineers stemming from deep within the companies who spend their off time, behind the scenes making things go faster, and work better just because they can. It’s the type of nerdy, yet respectable special project cars that often become the quirky sleepers of the world. Whether it’s a modern-day sleeper or one of the originals, the idea of subtlety tuning a car to achieve great speeds or other performance perks while flying under the radar has not been a lost art. There will always be a place for the classic sleeper and here are ten of the best of all time.

RELATED: The Best Sleeper Sedans For Under $15,000

10 2008 Audi S6

2008 blue Audi-S6
Front 3/4 view of blue 2008 Audi S6 driving. 

How about a Lamborghini in Audi’s clothing? That’s exactly what you’ll get with a 2008 Audi S6. This very understated mid-sized sedan is hiding a 5.2 liter V-10 sourced directly from Lamborghini’s (new at the time) Gallardo supercar. Here the engine made a respectable 435 horsepower, more than enough to propel the S6 to sixty miles per hour in under five seconds, which was plenty quick for a non-RS badged Audi from the mid-2000s.

During this time it wasn’t uncommon to see high cylinder count engines in sporty cars, but this was only the S model, and was styled as such. Later tuners famously uncorked the S6’s exhaust system and videos of Lamborghini-sounding Audi sedans filled the internet in a hilarious attempt at un-sleeping the ultimate Audi sleeper.

9 2001 Volkswagen Passat W8

2001 black Volkswagen-Passat W8 Wagon
Side view of black 2001 Volkswagen Passat W8 Wagon. 

A bit of an oddball, the 2001 Volkswagen Passat might be one of the sleepiest of sleepers. Volkswagen isn’t well known for its eight-cylinder engines, but that’s exactly what you got if you opted for the engine upgrade in your early 2000s Volkswagen Passat wagon. Available on this particular vehicle were options of either a sedan or wagon configuration, a manual transmission, “4-Motion” all-wheel-drive, and of course the famed W-8 engine that essentially combined two VR4s at a common crank to create the W-8.

This gave Volkswagen the flexibility to offer V-8 power, but in a more compact package. The Passat was the only car to ever use the 275 horsepower W-8 engine as Volkswagen discontinued it before switching to a more traditional V-8 engine.

8 2008 Pontiac G8 GT

2008 red Pontiac G8 GT
Front 3/4 view of red 2008 Pontiac G8 GT parked. 

Pontiac may be a thing of the past, but the G8, one of their last cars to be produced was a real winner. A sharp looking sedan on the outside, and fairly minimal on the inside, the G8 was undoubtedly a handsome thing. The base model was fairly ordinary with a V-6 powertrain, however, upgrade to the GT model and gone is the V-6 in favor of a Corvette-derived 6.0 liter V-8 that put out 361 horsepower and 385 pounds-feet of torque. It was fairly difficult to tell a GT model from a base model as the styling cues didn’t change much at all from model to model.

Upgraded wheels and quad exhaust tips differentiated the two, but from afar it was near impossible to tell if you were about to challenge a Corvette-powered G8 or not. Later Pontiac offered a slightly less sleepy GXP model with racier bumpers, and flashy wheels. In that model you got a punched out 6.2 liter V-8 now producing 415 horsepower. You also got access to a manual transmission. This thing was basically a hot-rod in fancy cop-car clothing.

RELATED: This Innocent-looking Vauxhall Corsa B Is the Definition of a Sleeper

7 2023 Lexus IS500

2022 gray Lexus-IS 500 F Sport Performance
Front 3/4 view of gray 2022 Lexus-IS 500 F Sport Performance parked. 

Every time a Lexus IS drives by, pinning it as a 350 or 500 is incredibly difficult. The styling changes are so minuscule that you’d have to either see the quad tailpipes, or hear the sound coming from them in the form of glorious 5.0 liter V-8 rumbles to tell its an IS500. Thankfully the team at Lexus hasn’t over badged it too. It’s full name of Lexus IS500 F-Sport performance might be silly and a sellout of calling it a full ISF, but it’s only badges say IS500, and from far away reading IS350 vs IS500 is difficult. This car is a true sleeper. It’s not even that loud at idle, but one crack of the throttle and 470+ horsepower are unleashed seemingly out of nowhere. It might be the ultimate daily driver, that you can, and should still buy today.

6 2003 Volvo V70 R

2003 blue Volvo V70 R
Front 3/4 view of blue 2003 Volvo V70 R parked. 

Although not the original go-fast Volvo wagon, the V70 R was the less obvious sleeper. It was also the one that arguably brought back the idea that fast Volvos could be taken seriously. Since the V70 R, beefed-up Volvo vehicles have been around in some form or another. R and R-design models have injected a sportiness to Volvo that hadn’t been seen in the decades before. After the R’s came polestar, which also bring subtle speed to the equation.

The Volvo V70 R might be one of the most subtle performance offerings from any brand ever, with the slightest of hints at its performance edge. A normal looking set of five-spoke wheels, and an extremely minimal rework of the bumpers are all that set it apart. It appears nearly as pedestrian as any other wagon on the road, and because of that, it makes an exceptional sleeper with nearly 300 horsepower from its aural inline-5 engine.

5 2012 Buick Regal GS

2012 white Buick Regal GS
Front 3/4 view of white 2012 Buick Regal GS driving. 

The Regal GS was undeniably beautiful. In the base model looks were only OK, but the GS model brought a luxurious feel to the car. Large wheels, a reworked bumper and body panels took the humble Regal and seemed to bring it up a class or two. It didn’t look particularly fast, but elevated elegance was more its thing.

The Regal GS was by no means a rocket ship, but it did offer a spicier 2.0-liter turbocharged engine that made 270 horsepower and nearly 300 pounds-feet of torque. For the time these were very healthy numbers for a two liter engine, even if it was a bit of a heavy-weight.

RELATED: 10 American Performance Cars That Can Be Classified As Ultimate Sleepers

4 2004 Mercedes-Benz E55 AMG (W211)

Silver 2004 Mercedes-Benz E55 AMG
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A front 3/4 shot of a 2004 Mercedes-Benz E55 AMG

The W210 E55 AMG was always going to be a tough act to follow, but come the early 2000s and Mercedes really did outdo themselves. Credited with being the super sedan that started the German horsepower wars that still wages onto this day, the W211 E55 AMG was a revelation. In fact, Doug DeMuro called it one of the greatest German performance sedans of all time. Built between 2003-2006, the W211 E55 packed a hand-built 5.5-liter Supercharged V-8, straight out of the SL of its day.

While the 469 horsepower may not sound like much by modern standards, the 516 pound-feet of torque and the soundtrack sure will impress. Power was routed exclusively to the rear wheels via a five-speed automatic gearbox. This humble-looking Merce could get to 60 mph in just 4.5 seconds and the top speed was limited to 155 mph. Take the limiter off and you're looking a 180 mph, making it the fastest production sedan of its day.

3 2004 Cadillac CTS V

2004 silver Cadillac CTS V
Front 3/4 view of silver 2004 Cadillac CTS V parked. 

A car no one expected from a brand with a shaky future. The original Cadillac CTS V launched the V performance division and might have helped bring some much needed youth-filled enthusiasm back to the brand known for catering to a more “seasoned” generation. Since then multiple generations of the CTS V have been produced, a smaller ATS, both of which have been replaced by the CT4, and CT5 V and now Blackwing models. Today, even an Escalade V exists, if you’re into that sort of thing. It’s been a bit of an alphabetical roller coaster, but the essence is still the same, take GM’s best powertrains, and build upon them whilst providing solid chassis tuning.

The cars aren’t particularly light, but they are always fast, and later V models tend to out handle the competition. V cars have traditionally been more restrained in the looks department and the very first V, the 2004 CTS V is the prime example. A set of chrome wheels, big brakes and shiny mesh grille are all that visually set the V apart from the normal CTS. You’d never know a 400 horsepower 5.7 liter Corvette engine lurks beneath.

2 1996 Ford Taurus SHO

1996 purple Ford Taurus SHO
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Front 3/4 view of purple 1996 Ford Taurus SHO parked. 

Get ready for the show, or SHO, rather. The third generation Ford Taurus SHO was something of a Frankenstein, and it's wonderfully awful, yet glorious at the same time. Known as the “bubble Taurus” because of its highly organic “bubbly” and oblong styling, it was the epitome of questionable 90s design. Looking back, however, there is a sort of nostalgia to the car as it, by today’s monotonous repetitive design culture seems like a breath of fresh (but odd) air.

This would be the third iteration of the SHO high performance model of the Taurus and Ford made sure to make it special under its plump skin. This time around the SHO would sport a V-8. Not just any V-8, but one with heads designed by engineering experts Yamaha, and the block from other engineering experts at Cosworth, a company Ford has worked with in the past on other racy models. This front-wheel-drive, V-8, oblong wonder was the epitome of a sleeper.

RELATED: The Best Sleeper Cars on the Market Today

1 1984 Mercedes-Benz 190E 2.3-16

1984 gray Mercedes-Benz 190E
Front 3/4 view of gray Mercedes-Benz 190E 2.3-16 parked. 

One of the most sought after sleepers in existence is the illustrious Mercedes-Benz 190E. In 2.3-16 guise, the 190E was the sleeper nobody asked for, but Mercedes needed to go racing. A homologation road car resulted and it’s so perfectly a sleepy race car derived sport sedan. The styling is so subtly different to the average eye that this car is exemplary of the times when badging (as it pertained to engine size) was relevant.

The 2.3 liter, 16 valve engine was a regulation-abiding capacity for four cylinder DTM racing edges of the time. 190E has, and will always stand as an early performance icon for Mercedes-Benz, and for the sleeper enthusiasts, it should be regarded as one of the best examples of the recipe.