European manufacturers have their unique way of bringing together extreme performance and unassuming looks, resulting in some of automotive history's most incredible sleeper cars. Manufacturers from all over the continent have made cars that look fairly sensible, discrete, and ordinary, but have performance figures that can worry some of the best sports cars! This was especially the case during the '90s and early '00s when ever-crazier Q-cars were being churned out by Europe's biggest manufacturers.
Lots of those cars have now become incredibly desirable. This list contains everything from slab-sided Swedish machines with powerful turbocharged engines to Teutonic autobahn killers and even a quirky slice of Frenchness! There's even a movie star in there, too, and what could be the greatest sleeper of all time.
10 Volvo 850R
Volvo has traditionally had an image as a solid, dependable family transporter. Whilst that's always been the case, Volvo has also made quite a few fire-breathing performance versions that have made for fantastic sleeper cars over the years! Perhaps the most classic Volvo sleeper car is the 850R. Available in both sedan and station wagon body styles, the 850R quickly gained a great reputation for being a car that combined performance and practicality without compromising on either of them. It even went racing, too! The 850R estate had a brief but very memorable run in the British Touring Car Championship and it's now regarded as one of the most iconic cars of the Super Touring era.
These days, the 850R has gone from a blink-and-you'll-miss-it sleeper to a bonafide classic. Thanks to collectors and enthusiasts demanding these cars, prices are continuing to go up. If you want to get your hands on one, you might want to do it now before it's too late!
9 Mercedes 500E
The W124 Mercedes E-Class is a byword in classic Mercedes dependability. It isn't exactly known for its performance. But, Mercedes did make an awesome performance version of it! The 500E was only available in mainland Europe and had the M119 5.0 liter V8. This was an engine that was typically found in the bigger S-Class, CL, and SL models. It also powered the CLK LM race car! As you'd expect, it made the 500E a fast sedan for its time. It could do the 0-62 sprint in 6.1 seconds and go onto an electronically limited top speed of 155 mph.
The 500E has become a holy grail of 1990s Mercedes models. It's not difficult to see why! It still looks very similar to a regular W124 E-Class, but it'll surprise everyone once you put your foot down and let that V8 roar.
8 Audi S4 (C4)
The Audi S4 has been a favorite sleeper car ever since it showed up back in the '90s. The C4 generation S4 looked barely any different from its normal brethren, but underneath the ordinary body shell was a turbocharged 2.2 liter 20v inline-5 engine. This engine put out 227 hp and it could take the S4 from 0-62 in 6.2 seconds! It was also given Audi's fantastic Quattro AWD system. For European customers who wanted a bit more power, the S4 Plus with its 276 hp V8 was available too.
This version of the S4 has become celebrated by Audi enthusiasts in the years since. It's not hard to see why, as it's a proper sleeper car that only those who know their Audis would be able to spot. It was also available in Avant station wagon form, making it one of the coolest family cars you could have!
7 Audi S6 (C4)
Like its S4 little brother, the C4-generation Audi S6 barely looked any different from a regular A6 but packed a real punch under the skin! The C4 S6 was available with the same engines as S4 and had a slightly slower 0-62 time of 6.7 seconds for the regular version. It also had the Quattro AWD system, like the S4, and was also available in Avant station wagon form.
As with the C4 S4, the C4 S6 has become beloved by Audi enthusiasts for its proper sleeper image and great performance. Combine that with proper load-lugging ability in the Avant version and the C4 S6 is pretty hard to beat!
6 Mercedes-Benz CL600 (C215)
(From the outside, the C215 Mercedes CL600 looks like an ordinary luxury coupe. If anything, it looks a bit boring! It's anything but boring under the skin, though. The CL600 was powered by the M275 6.0 liter twin-turbo V12. A development of the legendarily reliable M137 V12 from the '90s, the twin turbos allowed it to put out 493 hp in stock form. That was enough to accelerate the CL600 from 0-62 in 4.8 seconds and go onto an electronically limited top speed of 155 mph. Those kinds of performance figures could seriously worry some supercars back then!
If you want a big, luxurious European coupe with a discreet image and serious autobahn-crushing levels of power, there really isn't much better out there than the CL600. The big thirsty V12 might bankrupt you in fuel bills, but with a car like this, it's more about smiles per gallon than miles per gallon. That, and sounds absolutely amazing!
5 Renault Safrane Biturbo
Unless you're really into your French cars, there's a pretty good chance that you've never heard of the Renault Safrane Biturbo. Indeed, you might not have even heard of the Safrane in any way at all! But, Renault did make a big executive car back in the '90s and it was available with a twin-turbocharged version of the PRV V6 engine! The Safrane Biturbo put out 258 hp, had all-wheel drive, and was only available with a manual transmission. If that sounds like a recipe for a great driver's car, you'd be right!
The Safrane in any of its guises wasn't a success. This is probably due to it having the usual French car foibles, as well as being a victim of badge snobbery. The Biturbo also competed in a market segment where people wanted automatic transmissions and big V8 engines, so sales got hurt quite a lot. You'd be very lucky to find a Biturbo for sale anywhere. But, they are one of the coolest sleeper cars any European manufacturer has ever made.
4 Lancia Thema 8.32
Normally, the Lancia Thema is just a regular '90s sedan. The Thema 8.32, though, is a very different beast. For some reason, Lancia decided to put a Ferrari-designed V8 engine into this otherwise ordinary car. Specifically, it was the 2.9-liter Tipo F105L V8 that was used in Ferrari's 308 and Mondial models in the 1980s. The end result was a properly sporty sedan that most people wouldn't even take a second glance at!
The Thema 8.32 has become legendary amongst enthusiasts and when they come up for sale, they end up selling for big money. It's gained a similar status to the Mercedes 500E and for a very good reason!
3 Saab 9000 Aero
No other European car manufacturer has gained as much of a cult following as Saab has. There's a very good reason for that. Its regular models have always been great cars, but its faster Aero models have gone down in legend as proper sleeper machines. Perhaps the most overlooked of the Aeros is the 9000 Aero. The 9000 Aero had a turbocharged version of the 2.3-liter B234 inline-4-cylinder engine. Producing 222 hp, it could go from 0-62 in 6.7 seconds. Whilst that didn't make it the fastest performance sedan of its era, it had a unique character that its competitors didn't.
Saab 9000s are now being recognized as proper classics and, as a result, Aero models are on the verge of becoming collectors' buys. It's really not difficult to understand why. There's nothing quite like a fast Saab and there probably never will be again.
2 Audi S8 (D2)
In its regular guise, the Audi A8 is a sensible and understated luxury sedan. When it's the S8, though, it becomes one of the best sleeper cars around. The D2 S8 was powered by Audi's fantastic 4.2-liter V8, which put out 335 hp and took the car from 0-62 in 6.2 seconds in its initial tune. The engine was given a power boost to 364 hp in 1999, dropping the 0-62 time down to 5.6 seconds. Those are very impressive performance figures from a 1990s luxury car! The S8's appeal was boosted even more when it became one of the hero cars of the classic thriller Ronin.
No doubt thanks to its blistering performance and its appearance in Ronin, the D2 S8 has become an incredibly desirable car. Even people who aren't that into Audis would love to own one of these S8s!
1 Lotus Carlton/Lotus Omega
What list of European sleeper cars could be complete without the original European sleeper? The Lotus Carlton (or Lotus Omega if you're from mainland Europe) caused a huge stir when it came out in the early '90s. Lotus turned an ordinary executive sedan into a car that could leave some of the best sports cars of the time in the dust. It actually caused a huge scandal both within the car industry and with law enforcement agencies because of how fast it was! Because of that, it ended up being one of the first cars to be fitted with a 155-mph speed limiter.
People know what the Lotus Carlton/Lotus Omega is now, but back then it was a proper sleeper car. It's also one of the most desirable sleeper cars ever made, with values continuing to rise. Every single mad sports sedan from the '90s and '00s owes a lot to this crazy machine.