Sleepers are essentially cars whose appearance makes them dissipate into the crowd, but they have one trick up their sleeves—and that's performance. See, sleepers are the perfect tool to utilize for people who love to surprise sports cars they race; in other words, they might not look fast, but underneath their unassuming exterior is something magnificent.
For this list, we'll be focussing on some affordable sleepers that are already powerful right from the factory, but they can also be tuned to achieve even greater feats if that's the route you would rather travel.
10 2006 Mazdaspeed 6 ($8,000)
The Mazdaspeed name hasn't been used in many different Mazda models over the years, but the award for most tame-looking Mazdaspeed model has to go to the high-performance version of the Mazda 6. Every ounce of this car has been overengineered, well, except for its design of course. Underneath its hood was a turbocharged 2.3-liter inline-four that produced 274 hp, it also came equipped with larger brakes, a stiffer ride, and sticky tires.
The Mazdaspeed 6 could go from 0 to 60 in under 6 seconds, and go on to reach a top speed just shy of 150 mph. If for whatever reason, the Mazdaspeed 6 is too large for your liking, $8,000 is too cheap for you, or you prefer your dishes served in a more compact, more fashionable form, the Mazdaspeed 3 is an excellent alternative.
9 2006 Volvo S60 R ($10,900)
Volvo is no stranger to creating fast unassuming vehicles, look at the new XC60 SUV for example, but one of their most praised creations was the S60 R. As always, Volvo's main priority lies in the safety and good crash test scores. On top of that, you can buy a fast S60 R for under $11,000.
It had a 2.5-liter inline-five motor capable of producing 300 hp, and with that figure comes an all-wheel-drive, a 6-speed standard transmission, as well as Brembo brakes, and an adjustable suspension configuration. If there were ever a car that perfectly encapsulated a racecar-driving-grandpa, the Volvo S60 R would be it.
8 2004 Audi S4 ($8,000)
Audi falls into the other German luxury car manufacturers like BMW and Mercedes-Benz's playground, but never receives as much love as the other two brands. However, back in 2004, Audi's S4 made them tremble in fear. As standard, the S4 came fitted with Quattro all-wheel-drive deeming it the far superior choice when it came to harsh weather conditions, but not only was it practical, it was fast too.
Under the small Audi's hood was a naturally-aspirated 339 hp 4.2-liter V8, and that deemed it fit to achieve a 0-60 time of just above 5 seconds. So, the Audi might not have sported as an exciting design language as its other German rivals... but isn't that the point of a sleeper? CarGurus has a 2004 S4 for sale at the moment for just $8,000 if you were looking for a steal.
7 2008 Lexus IS 350 ($10,000)
Lexus has always been known for creating high-quality cars, but only certain models stand out performance-wise from the rest of their line-up like the LFA or new IS 500 F Sport, but back in 2007, the IS 350 was seen as just an ordinary JDM vehicle with a solid interior. What most people neglect is that these IS models were true sleepers, and are more affordable than ever in today's used market.
Its front-mounted 3.5-liter V6 engine jolted out more than 300 horsepower, and since all this power was sent to the rear wheels, it wasn't just a fast car, but a fun and tossable one as well. With a majority of the entries on this list, you'd be sacrificing a sense of comfort or refinement and receive performance in return, but the IS 350 still comes with advanced safety technology, a paddle-shift gearbox, and a supple leather cockpit.
6 2008 BMW 335i ($7,000)
Whether you decide to pick yourself up an E90 sedan, or an E92 coupe, the 335i is a Bavarian powerhouse capable of things no one would have ever could imagine, and it's all thanks to the legendary N54 motor. The N54 was a 3.0-liter twin-turbocharged straight-six with immense tuning capabilities, and a factory power output of 300 hp and 300 lb-ft of torque on the dot.
In comparison to other entries, the 300-hp figures seem like nothing out of the ordinary, but BMW's engineers designed the twin-turbo layout in such a way, that there would be virtually no turbo-lag. The standard 335i was rear-wheel-drive making driving sideways a breeze, but there was also an optional xDrive variant that sent power to all four wheels maximizing grip on pull-aways. The E90 and E92 generation 3 Series has a reputation for being a tad unreliable, so when shopping for one, remember a 335i worth $7,000 might cost a bit extra to keep running smoothly.
5 2012 Ford Taurus SHO
The original Ford Taurus SHO paved the way for all other sleeper cars to come, and the 2012 year model SHO embodies its ancestor's name in a perfect fashion. For the average motorist, the Taurus SHO looks like every old ordinary American sedan on the road, especially in silver, but its 3.5-liter turbo-V6 has another story to tell.
The SHO combines the blistering acceleration of an all-wheel-drive system with its 365 hp, and 350 lb-ft of torque to create an average-looking sedan capable of reaching 60 mph from a standstill in as little as 5.2 seconds and can zoom past most cars on the road with little hassle. For $9,000, you'll be driving one of the road's most subtle sleepers on the market today.
4 2004 Pontiac GTO ($13,000)
In a world filled with heavily depreciated foreign sports cars, it seems as if there is almost no reason to choose an American pony car over German luxury. While that statement might be true to an extent, it's all about what's underneath the GTO, not fancy leather or ground-breaking technological feats, rather sheer power.
It engulved a LS2 6.0-liter V8 with 400 hp and 400 lb-ft of torque, you'd never expect those numbers to be associated with a Pontiac product, but those numbers weren't just for bragging rights. See, the GTO could put its power down at any time thanks to its Tremec T56 gearbox resulting in a hefty pullaway at all times. CarGurus just had a 90,000-mile GTO arrive on their website, and is listed for $13,000.
3 2006 Porsche Cayenne Turbo S ($13,000)
What type of list would this be if we were not to include a ludicrously fast SUV, in this particular case, the Porsche Cayenne Turbo S. Let's talk numbers: 520 hp and 530 lb-ft of torque from a twin-turbo 4.5-liter V8 engine, all-wheel-drive, and a 5,200 lb curb weight. Yes, it's a rather heavy car, but those phenomenal power figures allow this German SUV to catapult from stationary to 60 mph in just 4.8 seconds deeming it quicker than most of our list.
Not to mention, it's actually a very capable off-roader too, so this isn't one of those pavement princesses some manufacturers create. So, to conclude, the Cayenne Turbo S is blisteringly quick, looks like an ordinary ugly Cayenne, can be driven off-road, and costs upwards of $13,000, what more could you want?
2 2007 Audi S6 ($14,000)
Let's address the main selling point of the C6-generation Audi S6 immediately, its Lamborghini-derived V10 engine. Yes, you heard that right, you can buy a used V10-powered luxury German automobile without spending more than $14,000... excluding maintenance costs of course. A few years after Audi seized ownership of Lamborghini they borrowed the 5.2-liter V10 from the Lamborghini Gallardo and put it into their R8 supercar, as well as their luxury family saloon, the S6.
This harmonious engine pumped out a pulverizing 435 hp, this resulted in a luxurious German limousine with a 0-60 time of fewer than 5 seconds, and a scream that will wake up the entire neighborhood. Sure, the S6 might not be much of a surprise after hearing its stats and engine noise, but based on pure appearance alone, no one would ever know you'd be driving an old four-door Lamborghini.
1 2005 Mercedes-Benz E55 AMG ($16,000)
All Mercedes-Benz sedans look the same, and this philosophy has been proven for decades, even the new S-, E-, and C-Class cars feature almost undifferentiated looks. Back in 2005, Mercedes took things even a step further, if it wasn't for the quad-exhaust pipes and the V8 Kompressor badge on the side, it would be almost impossible to distinguish an E 55 from a standard E 200.
What does that Kompressor badge mean, you might ask: It means that there's a gorgeous supercharged 5.4-liter V8 lurking underneath the hood spouting out 475 hp and 520 lb-ft of torque to the rear wheels. These incredible power figures allowed the E 55 to zoom to 60 mph from nothing in only 4.6 seconds ranking it quickest on our list. E55 AMG models are currently for sale from around $16,000, but it looks as if prices are destined to skyrocket in the near future.