Evolution is a hell of a thing. In science, it means that an organism has become better suited to its environment. In automotive technology, it’s often represented as vehicles being altered to adhere better to changing safety and fuel economy regulations.
Sometimes, though, it happens when there is a lack of regulations. Like sporty German sedans that are designed to eat up miles at high speed on their home country’s de-restricted stretches of autobahn, and look understatedly cool doing it. There have been a bunch of extra-freaking-cool examples of German stealth sedans over the years, but one in particular that’s often overlooked is among the best: The C5-generation Audi RS 6, which was sold in the USA for just the 2003 model year.
Here’s what makes this mighty full-size sedan a rare legend, as well as something to be careful with if you ever consider picking one up for yourself. 
Audi
Big on Everything
After years of American enthusiasts craving a proper Audi RS model, the C5 RS 6 was the first to be sold in our nation’s dealer showrooms. Slightly lesser S models were great and all—says the B5-generation S4 owner—but we never got anything from the four-ringed brand offering the pinnacle of performance, the widest wheel arches, and a handful of satin metallic exterior accouterments to show it all off.
Considering the RS 6’s epic stats for its era, I ain’t mad. Under its hood is a 90-degree Cosworth-built 4.2-liter V8 sporting twin turbos and a forged steel crankshaft. Power output is rated at 450 horsepower and 415 pound-feet of torque. A five-speed ZF automatic transmission was the only option for sending all this power to its Quattro all-wheel drive system, which Audi says is due to it being the only unit that could take all that power.
The C5 was heavy for its era at 4,229 pounds, but with 450 horsepower on tap, a mid-four-second 0-60 run is quite possible, and 0-100 happens in just over 10. Luckily, its brakes are up to snuff: eight-piston calipers clamp down on 14.4-inch rotors up front, whereas a big single-piston unit grabs a hold of 13.2 inches out back.
Outside of big stats, it’s a generally big sedan for its era, too, sporting wider wheel arches than the standard A6, bigger front bumper inlets to feed its intercoolers and aid cooling, plus an overall sportier body kit.
Car and Driver named it the winner in a comparison with the BMW M5, Jaguar S-Type R, and Mercedes-Benz E55 AMG.
“Flat cornering, plus Super Glue adhesion, plus beautifully weighted steering, plus abundant power, plus monster brakes—the front calipers grip with eight pistons—make the RS 6 a supremely composed performer at high speeds,” the late Tony Swan wrote. “It inspires confidence that goes beyond its rivals’—an endearing trait in a car in this performance category.”
High praise, and sadly, Audi only sold 1,435 of them in the USA. That means it’s good-looking, potent, and rare—a recipe for enthusiast success for sure.
Surprisingly Inexpensive For Its Rarity
If you’re a blue-sky-thinking, curious early 2000s car connoisseur like yours truly, the next step after going through these stats and impressions is taking a gander at Craigslist, Facebook Marketplace, and every other fine (and not-so-fine) method of hosting used car for sale ads.
It can be tough to find examples in general, though, due to the under-1,500-units-sold part. By comparison, nearly 10,000 E39 M5s were sold in the USA over its four-year run. Its tough finding W211 E55 AMG production numbers, but it looks like just under 8,000 were produced worldwide.
C5 RS 6s can be surprisingly cheap. A quick perusal of Classic.com reveals an average sale price of $18,463—OK, that’s not exactly cheap—but the lowest sale is just $7,600. That’s more my speed, though, there could be some sketchiness at that level. But why the massive spread?
One word: Audi. Well, actually, maybe two: Audi complexity. Don’t get me wrong, I’m always up for a challenge, especially after being conditioned for complexity with my S4. But there are things about the mighty RS 6 that could be a real buzzkill.
But Here’s What Makes It a Legend in Other Ways
There’s a lot going on behind the C5 RS 6’s front bumper, and it all requires attentive maintenance. The thing may be a big full-size sedan, but all that under-hood space is occupied by a biggish V8 with two turbos hanging off each side. It’s time-consuming to perform jobs that are otherwise much quicker on other platforms. By the way, servicing or replacing either or both turbos is an engine-out job. Then there’s its timing belt service, which is a measly 35,000 miles or three years, whichever comes first. And it’s a good idea to do a bunch of stuff while you’re in there, like various tensioners and the water pump.
The transmissions are infamously weak as well, apparently, they could barely take all that power from the factory. Dedicated enthusiasts have thrown in upgraded components or swapped to six-speed manual units with a sturdy clutch and flywheel combo. Otherwise, regular fluid changes are a must.
Then, more general servicing quickly gets pricy: The engine takes nine liters of full-synthetic oil. Though, the German parts tax doesn’t seem as bad as it used to be with a bunch of retailers in the game these days. Old cars mean old rubber, and old turbocharged German engines have a mess of rubber vacuum lines under their hoods that are often the source of random issues.
The RS 6 sports hydraulically actuated suspension that reduces body roll in the twisties, too. I’m shuddering at the thought of having to troubleshoot that, but luckily there are plenty of aftermarket coilover options that do away with it and avoid any potential headaches entirely. Finally, who can forget the many, many bushings tied up in the RS 6’s front double-wishbone and rear multi-link suspension?
Still, I’d Love to Own One, And I Bet Some of You Would, Too
Despite the C5 Audi RS 6’s ability to rob you blind, there are ways to potentially avoid it. Service history, any indication of attentive ownership, an open mind, finding the cleanest example one can for their money—all stuff that applies to keeping a cool and critical head about navigating the used car market in general, but it really helps here. Then, there’s expectations: If you’re salivating over a particularly cheap example, be ready for a world of pain (or a thorough lesson in DIY maintenance). A well-cared-for, higher-priced example might never cause any headaches at all … though, I’d hate to be too optimistic.
Like any enthusiast vehicle, I wouldn’t be afraid of miles if there was ample service history. Hell, if one’s got 170K or more and running well, there’s a good chance it’s been looked after, because it surely would’ve been mechanically totaled by then if it wasn’t.
The juice could definitely be worth the squeeze, and I’d love to find out someday. This muscular sedan looks great, it’s a total monster, and it comes from an era of German engineering that’s known for wonderfully solid and confident ride quality. It has the ability to rip down the highway at massive speeds in total comfort, and just oozes sense-of-occasion.
We can’t forget the aftermarket, either—apparently, over 500 horsepower is as easy as an ECU tune. Though, I’m not sure that’s the best idea considering its transmission situation.
I actually got to very briefly drive one while in high school in the mid-aughts. A friend’s dad owned one, and let her borrow it to come hang out one summer night. Knowing my buddy and I loved all-things VW and Audi, she threw me the key and let me take it for a spin. I’ll never forget pulling up to a long, empty, straight road and dumping the throttle; it was my first time experiencing something properly fast.
Makes me wonder if my career in automotive journalism has just been one long, drawn out quest of chasing that high. If I ever pick one up for myself, hopefully it’ll be less financially damaging than a high brought on by illicit drugs. Hopefully.
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