In motorhead parlance a sleeper is a car that looks like a regular car, nothing special, but when the driver steps on the right foot pedal, it goes like spit. Often, this is applied to someone who has souped up a grocery getter with a big-block engine and gone out looking for people to underestimate their build. A chassis-twisting engine in a family car that has a big engine bay and a surprisingly lightweight build can make for a drag car no one will see coming.

Leaving people at the line is only one of the advantages, especially if you're up to no good. That flashy flame-covered GTO Judge or fender-flared BMW is going to attract tickets like a light attracts moths. But the LTD wagon that's been stripped down and had a 454 hidden beneath its mammoth hood? Who's going to believe that's ripping down the public roadways?

It's not just hot rodders that build sleepers; manufacturers have been known to get in the game as well. From American car companies sneaking racing engines into factory cars for homologation reasons or Mercedes-Benz engineers answering the question "What happens if we put the 6.3-liter engine from our limousine in our sedans?" Sometimes, it's as simple as deciding that just because you want to carry four passengers and groceries doesn't mean that you're dead inside; you can still enjoy a little extra power. Whatever the reason, there are some cars out there that might be hiding a little bit of their oomph from prying eyes. Here are some sleepers you might not be paying enough attention to.

25 Buick Regal GS

via buick.com

Buick has a long history of hot rods dressed up as mid-level luxury sedans and coupes. The most legendary these days is the mid-eighties turbocharged GSX. These days, Buick has more or less been relegated as 'that GM brand that does well in China'. The advertising for Buick says it all, focusing on how no one can pick out a Buick in a crowd. So, it's easy for a Buick to get sleeper status. For the GS, it does that with a modern muscle-car-worthy V6 putting out 310 hp that'll shoot the all-wheel sedan to 60 in 5.4 seconds.

24 Volvo V70 R

via autogefuehl.de

For years, all people knew about Volvo was that they were safe and that they were shaped like a box. The truth is that they have a long history of also building fast cars. Being reserved practical Swedish folk, however, they don't always advertise that.

Their legendary 242 Turbo is remarkable not only for its speed but also for the fact that it looks like the dumpiest station wagon around.

The V70 R has carried on that tradition with an all-wheel drive powered by a five-cylinder engine just under three hundred horsepower driven by a proper six-speed transmission, all in a simple station wagon design no one will see coming—unless they know what Volvo gets up to.

23 Mercury Marauder

via performance.ford.com

The Ford/Mercury/Lincoln Panther platform was more or less the last holdout for the body-on-frame three-box design that was the American car since the '50s. They served as taxis, airport cars, police cars, general fleet cars—whatever you needed with four doors and relative comfort and was also mass produced. They weren't exciting per se. They were just functional.

For the swan song of the platform under the Mercury brand, they took every hot part from every Panther car so far to create a hot rod Marauder.

While the factory model still leaves something to be desired in its mid-7-second 0-60 run, like a proper muscle car, it has enough potential for the shade tree mechanic to bolt on the go-fast bits for one last Mercury muscle car.

22 Chevrolet Cobalt SS

via caranddriver.com

For most people, the Cobalt barely made an impression at all. It came and went with little fanfare, and most people would be hard-pressed to pick it out of a lineup of Chevy compacts. That's not due to a lack of praise, however. Car and Driver rated it top of the class among the Corolla and Civic in its base form. For the SS, they added a supercharger cresting the little car to over 200 horsepower with the handling to match. This is one I've driven, and I have to concur. I was prepared to be bored senseless in this car but found it a delight to drive, with the only hint that it's hiding something being the odd garish wing.

21 Chevrolet SS

via motor1.com

For decades, the sedan banner for Chevy was carried by the Malibu and the Impala badges. In various forms, the Malibu or the Impala would carry the 'Super Sport' badge, indicating that the boys back at GM had shoehorned some extra power into the otherwise family car. In 2014, Chevy decided to make the SS a car unto itself—not a Malibu SS or an Impala SS, though essentially it was. Just an SS. Maybe it was because they thought no one would buy a $50,000 Malibu even if it did have a 415 hp engine and a 0-60 hustle of 4.5 seconds. Whatever the reason was, it didn't work because the car went away in 2017 without many knowing that the simple Malibu looks hid Camaro-style go.

20 Volvo V60 Polestar

via youtube.com

Most companies have an in-house set of engineers, a group of mad scientists whose job it is to squeeze out an extra amount of power and performance out of their cars. For Ford, it's the Special Vehicle Operations or SVO. Subaru has the STi division; Toyota, the TRD; Mercedes-Benz, the legendary AMG; and BMW, the simple but iconic M. For Volvo, that division is Polestar. While it lacks the mechanical menace of a set of initials, they're no less addicted to speed. For the V60, Volvo's small wagon, that means massaging an engine to 362 hp and a 0-60 time of 4.4 seconds in something that still looks like a small Volvo wagon.

19 Honda Accord 2.0T

via automobilemag.com

Not all sleepers are a product of sly engineering or special editions. Sometimes, in the process of making a normal economy sedan, a company just happens to believe a competent engine should be included. Honda has been a lot of things for a lot of years. They've been known for small economic cars, but they've also had a presence in racing, including Formula 1 since the '60s. With one foot in racing and one in economy, it's only natural that the two will meet from time to time. For the unassuming Accord, that means it hides a 252 hp engine capable of taking it to 60 in 5.5 seconds.

18 Mercedes-Benz 500E

via roadandtrack.com

Porsche has a long history with Mercedes-Benz that predates the brand Porsche. Before there was a Porsche or even a Volkswagen, Doctor Ferdinand Porsche worked at Mercedes where he designed the first hybrid car decades before the Honda Insight.

Once the Porsche brand existed, however, Porsche and Mercedes were more likely to be track rivals than collaborators.

In the early '90s, however, before AMG had established its badge for factory hot Mercedes-Benzes, they turned to Porsche to help build a hot version of their sedan. This meant warming over the 500SL engine and strengthening the suspension in what otherwise looked like a normal 500 sedan.

17 Volkswagen Golf R

via autoweek.com

The Golf, or "Rabbit" as it was initially known in the US, was the water-cooled successor to Volkswagen's super successful Beetle. A simple and affordable car for the masses, the Golf was meant to be the new people's car. Eventually, the good folks at Volkswagen thought they'd make a hot version of the Golf called the "GTi," and the hot hatch was born. For years, the GTi was enough, but there's always faster. First, that meant boring out the already potent 2.8-liter VR6 engine to 3.2 liters and running it through an all-wheel-drive system for the R32. Now, that banner is carried by the Golf R with a turbocharged 2.0-liter four-cylinder good for 292 hp that only the faithful can tell from a regular Golf.

16 Mazdaspeed 3

via davisenterprise.com

Mazda sometimes likes to keep things simple. For instance, their mad-science division is simply and straightforward-sounding Mazdaspeed. For the 3 series hatches, they entered the hot-hatch market with the Mazdaspeed 3. While not as subdued as the Golf in the looks department, all Mazdas had the wild look with excessive lines and edges. The Mazdaspeed 3 had a 262 hp engine, though since it still went through the front tires, it was subject to a fair amount of torque steer—a small price to pay for an otherwise lively hot hatch that looks like someone's college ride.

15 Audi RS6 Wagon

via carsbase.com

Audi already has a performance moniker with the "S" models of their cars. Those "S" sedans became popular in the car-chase movie Ronin and The Transporter. While the S8 became the fantasy executive getaway car and the S4 became the underdog competitor to the M3, the engineers at Audi decided they could do even better. In the '90s, Audi got with Porsche and hot-rodded their 2 wagon to create the RS2. The ultimate expression of the RS also comes in wagon form with the RS6 Avant at 597 hp, meaning that you and your dogs can launch to 60 in well under 4 seconds on your way to a 189 mph top speed.

14 Pontiac G8 GXP

via topspeed.com

Pontiac, in its waning years, really tried to live up to its slogan of building excitement. They started rebadging Australian Holden muscle cars and even tried to revive the GTO label. Their swan song was another such reworked Holden, the G8 GXP with a Corvette LS3 engine good for 415 hp in a kind of plain-looking sedan package. This results in a launch to 60 in 4.7 seconds. Unfortunately, this car was a 2009 model, just in time for the American automotive industry to crash. With Pontiac gone to history, now, GM relies on Cadillac to be their Corvette-powered sedan home.

13 Lotus Carlton

1992 Lotus Carlton
via cargurus.com

It's not the best-known car in the United States. Somewhere deep down in the hundreds of cars lists, you might find one in Forza for the X-Box, but when one shows up for real in the States, publications like Road & Track and Jalopnik take notice. For most Americans, a Carlton is a silly dance and a cousin to the Fresh Prince of Bel Air. For Brits, it's a frumpy sedan from Vauxhall. Lotus got a hold of the Carlton and not only tuned the turbocharged engine to 377 hp but also made sure the sedan could handle those speeds, which were in supercar range in the 1990s.

12 1987 Shelby Omni GLHS

via motor1.com

Once the Volkswagen GTi was released, the hot-hatch races were on. In the United States, at least manufacturers didn't have to deal with competition from European manufacturers, except for the Peugeot 206, but the GTi was more than enough competition.

Since Carol Shelby had followed Lee Iacocca to Chrysler, he started doing what Shelby did best: putting big engines in small cars. Those efforts resulted in the otherwise bland and forgettable Omni getting the GLH edition, which stands for "Goes Like Hell." Not content, Shelby found "s'more" and the Omni GLHS (Goes Like Hell S'more) with 175 hp and 175 lbs of torque was born. Only 500 of these surprise hot hatches were made.

11 Saab 9-2X

via autoevolution.com

For years, Saab had quietly been that other oddball Swedish car maker who also happened to make fighter jets. In what would turn out to be a reckless expansion, Saab was bought out in the 1990s, and its distinctive car designs were brought more in line with the mainstream as it started to share platforms. One of the cars that it ended up sharing with, however, was the Subaru Impreza WRX, which was earning its reputation as a road-going rally legend. Car and Driver rated it as WRX performance but with a better package.

10 Dodge Neon SRT4 Turbo

via highrollershotrods.com

The Neon, in some ways, might be a victim of its own popularity. The compact entry-level Dodge/Chrysler was a success, meaning that there were a lot of the affordable cars around to be unloved hand-me-down cars that maybe weren't the most exciting. That makes for a great sleeper, however, like with the turbocharged SRT4 with its 230 hp that hauls the car to 60 in 5.3 seconds. With just the hood scoop and the tall Superbird-esque wing to give the car away, it's enough to surprise even WRX drivers.

9 Mercedes-Benz R63 AMG

via autoweek.com

The Mercedes-Benz R-class is already a hard beast to get a handle on. It's somewhere between a minivan and an SUV that seats six. There's such a thing as a hot SUV, but there aren't many examples of a hot minivan.

So, it might be the SUV side of the 'sports tourer,' as Mercedes refers to it, that got the 507 hp AMG treatment.

All R-classes are all-wheel drive, and the AMG is no different. This combination makes it good to 60 in just over four seconds. Due to our lack of Autobahns and a reasonable argument for this kind of speed, the R63 was only available as a special-order package that wasn't advertised, so it's even more of a sleeper in that, for some, they didn't even know it was an option.

8 Ford Taurus SHO

via motortrend.com

The Ford Taurus might be able to answer the question of when a sleeper is no longer a sleeper. There was a massive distance between the unremarkable stock Taurus and the wild SHO. The SHO or Super High Output came into being when Yamaha got a hold of a Ford V6 and warmed it over for transverse mounting. Originally, it was going to be a limited-run car, but it proved popular enough to last from 1989 to 1999. In 2010, it was revived and lives on today, offering Mustang performance in an unassuming four-door. The car has a loyal following making it a popular 'sleeper.'

7 Subaru Forester XT

via youtube.com

Everyone knows the WRX, the hot Subaru from the World Rally Championship. There's nothing about the garish WRX that sleeps; its angular box flairs and wings and meaty tires all scream that it's a slightly tamed race car with a backseat. This is a departure from the rest of the Subaru models, however. Those are the frumpy and workaday cars of NPR listeners and snow town residents.

The Forester, their tall station wagon or SUV offering, is exactly that, except when it came in the XT package.

While it only rated 210 hp on the window sticker, it continually tested 0-60 times in the Porsche Boxster range of 5.3 seconds, all while continuing to look like the librarian's commuter car.

6 1993 Saab 9000

via sasab.com

The Saab 9000 isn't that dynamic a car. It's the tamer big brother to the 900 Turbo, but it has one advantage: it's really durable—perhaps, a ridiculous amount of durable. This means that the engine can take a lot of abuse. A durable engine that can take abuse can also take mods. A Jalopnik reader gave them a shopping list to build out a 500 hp Saab 9000 including "a holset hx35, 1000cc+ injectors, walbro 255, cams, Volvo valve springs, uprated clutch, intercooler, new head gasket." Some modifications to the exhaust, and you're off to the races in a simple-looking Swedish sedan.