Sleeper cars are vehicles that look assuming but are packing some serious muscle under the hood. They reach super car-baiting speed and are truly great performers. In history, there have been some really interesting sleeper cars. Cars like the Audi RS2 and the Mercedes 500E are interesting and are definitely unassuming.

Related: 10 Best Sleeper Cars, Ranked

This list will explore some of the coolest sleeper cars. From brands like Audi to BMW, there have been some absolutely fantastic sleeper cars that are so unassuming that many don't often give them a second look. But when they do, they realize how cool of a car that exists underneath.

8 Saab 9-2X

 Saab 9-2X
Via Consumer Guide Auto

The Saab 9-2X was a car that was made by Subaru but was marketed as a Saab. The 9-2X featured some redesigns done by Saab, making the car look more in line with the brand's design ethos. This included an update to the front and rear styling on the exterior.

 Saab 9-2X
Via Autoevolution

The car was also pretty powerful, with 165 bhp for the 'Linear' edition and 227 bhp for the 'Aero' edition. The Aero edition featured a Subaru WRX turbocharged 2.0-liter engine. The car is cool because the vehicle is heavily based on the WRX and doesn't look as powerful as it is.

7 Lancia Thema 8:32

Lancia Thema 8.32
Via Motoring Research

The 8:32 in the Lancia Thema stands for 8 cylinders and 32 valves that are in the engine. Despite not being the most exciting car to look at, it was actually very fast. Using a Ferrari V8, the car put out 215 bhp to the front wheels.

Related: Here's Why You Should Care About The Lancia Thema 8.32 

1987 Lancia Thema 8.32
BangShift

The Lancia Thema is immensely cool, not only with its engine but with the fact that it reaches 149 mph at top speed. Using a Ferrari engine but not coming with the price of a Ferrari, it was a great car, and despite there being some minor issues with understeer, it definitely deserves a place on this list. It was also the first production car to be fitted with an active aero spoiler.

6 Lexus IS 300

 2004 Lexus IS 300
Via ForceGT

The same engine used in the Toyota Supra Mk IV was used in the Lexus IS 300, which is very impressive. The Lexus IS 300 is truly a shockingly powerful car and upon first impressions, it is definitely an unassuming vehicle. Many enthusiasts love the 2JZ engine, and it is especially big with enthusiasts when it comes to tuning.

Related: The Best & Worst Lexus Models, Ranked 

 2004 Lexus IS 300
Via topspeed.com

The IS 300 has 215 bhp, which is definitely a surprise in such an unassuming car like this. As such, it remains to be one cool sleeper car and is enjoyed by many.

5 Audi S6 V10

2009 Audi S6 V10
Via Youtube

Audi's third generation of the S6, launched in 2006, came with an amazing engine in an unassuming exterior look. Equipped with a Lamborghini Odd firing 5.2-liter V10 engine, the car is fantastic. The same engine is used in the Lamborghini Gallardo, with some changes made to the powertrain in the Audi.

Related: 10 Of The Best Audi Car Models On The Market 

Audi S6 V10
Via Autoevolution

The 429 bhp combined with the 155.3-mph top speed means that the Audi S6 makes a comfortable appearance on this list. Its credentials are top marks for being a fantastic sleeper car that looks extremely unassuming.

4 BMW 550i

 2008 BMW 550i
Via: www.barrett-jackson.com

Launched in 2003, the 550i is a fantastic sleeper car. The car is no exception to the brilliant engineering done by BMW. It is truly a balanced vehicle and the driver does feel fully immersed with the 550i. The styling of the car is fantastic, with the high quality of BMW shining through.

 2008 BMW 550i

The car is a great sleeper car and its credentials speak for themselves. There are many engines available in the BMW, making it great for a diverse choice and it feels sporty, leading to an enjoyable drive for owners.

3 Mercedes 300 SEL 6.3

 Mercedes Benz 300 SEL 6.3
Via: favcars.com

The Mercedes 300 SEL was a luxury car launched in 1968. The engine was massive and was extremely powerful. The engine was a 6.3-liter M100 V8, which was also featured in the 600 limousine. Upon its release, it was the fastest four-door car in the world.

Mercedes Benz 300 SEL 6.3
Via Carscoops

It was definitely unassuming as it was a full-size luxury car that looked like it would be so heavy that it wouldn't go fast. Going 124 mph at top speed was extremely impressive, and the car could do this comfortably. It is definitely one of the coolest cars on this list.

2 BMW M5 E28

BMW E28 M5 for sale
Classic Trader

The BMW M5 E28 is a great car that wasn't exactly deemed the most impressive when it was launched, but it is truly iconic. Being sold as a super sedan, the car was also powerful and its 278 bhp was more than the Ferrari 328 that existed at the same time.

 BMW M5 E28
motor1.com

It was incredibly expensive too, which badly affected the car's sales. However, it had fantastic ability and its 151 mph top speed was astounding in a car like this. It is definitely one of the coolest ever sleeper cars that we can think of and is truly a reflection of BMW's rich engineering.

1 Ford Taurus SHO

 Ford Taurus SHO
via Motor1

The Ford Taurus SHO is definitely one of the most unassuming cars on this list. Its second-generation launched in 1992 was deemed boring. The Taurus SHO, however, proves that sometimes, looks aren't everything.

Ford Taurus SHO
Via en.wheelsage.org

The engine was a Yamaha-built V6 and was truly amazing with its 220 bhp. It was impressive through going 0-60 mph in 7.9 seconds - definitely fantastic for a sleeper car such as this one. Ford definitely made the SHO live up to its full name, 'Super High Output.'

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