A state-of-the-art front or four-wheel drive chassis; elegant, well-proportioned looks, superb build-quality and, so far, good reliability. Equipment levels are high but you won't buy an S4 for its showroom appeal. The RS4 apart, it's hard to think of another sports saloon or estate that could rush you front point to point on any roads in any weather quite as quickly. According to Audi's technical people, the 2.7-litre engine develops so much torque that they couldn't find an automatic gearbox capable of taking it. This is one reason for a slightly heavy clutch which, for the uninitiated, can make the change from 1st gear to 2nd somewhat jerky.
The V8 car is a real work of art. Pop the bonnet and it seems as if Audi have put a quart in a pint pot, the big V8 filling the bay to such an extent that there's little more than finger width around its perimeter. It wasn't merely a case of taking the 4.2-litre V8 from the A8 and bolting it into the A4. It has been thoroughly re-engineered, with all the mechanicals responsible for driving the pumps, valve gear and so on taken from the front of the engine and squeezed into a gap at the back between the engine block and the flywheel. The net result is a far more compact arrangement, but Audi have also aimed at cutting weight. With lighter pistons and conrods, this engine weighs no more than the old S4's twin turbo V6.
The interior is what we've come to expect from Audi. Beautifully screwed together, predominantly black and styled with effortless cool, the S4's only Achilles heel in this instance is that the driving position feels a little too high. Some may grumble that the interior is too similar to any other A4 and having seen the design direction Audi have taken with the A8, perhaps this generation A4 is the last to go down the minimalist 'black is best' route.
There's precious little data available for the V8 models so let's concentrate on the 2.7-litre car. The big ticket check is the state of the turbochargers. If you see white smoke emitting from the exhaust, walk away. A cooked turbo will set you back somewhere in the region of £3,500 to fix. Throttle body boots are prone to tears and the turbo bypass valves are known to fall off. Driver's seats have been known to rock back and forth due to play developing in the track and the windscreen washer pump can crack. Careless gear shifting can also damage the synchromesh on six-speed cars. The most common complaint amongst S4 owners, however, are warped front brake discs. A combination of factors including poor material strength, large swept area and inadequate cooling means that a session spent on a track that's hard on brakes can deform the discs. If the car judders under mild braking as if the ABS is intervening early, you're looking at warped discs. A set of decent aftermarket discs will alleviate this issue but you'll be looking at a replacement cost of around £180 for a decent set. Unless it's been cornered with extreme prejudice, the S4 is surprisingly gentle on tyres but it doesn't hurt to check as replacements will be costly.
(approx based on an 1998 S4 2.7) A clutch assembly kit will be around £225 and an alternator should be close to £170 and a radiator around £130. Front brake pads are around £85, rear brake pads will be £65, a replacement headlamp lens is close to £30 and a starter motor close to £145.
The 2.7-litre S4 is powered by a 265bhp twin-turbocharged V6 engine capable of rest to sixty in under 5.5s on the way to an artificially limited maximum of 155mph. A six-speed close-ratio gearbox. And quattro four-wheel drive, so that, unlike your rival M3 driver, you can get all that power onto the tarmac. To ride in, the S4 is more akin to the softer-sprung Mercedes C32AMG; yes, you can attack the country lanes but there isn't the drawback of a fidgety ride on the motorway. Technically, the S4 is little different from the A4 2.8 quattro Sport, apart from the addition of uprated dampers to curb high-speed body movement. As long as you can live with the car's thirst and sonorous exhaust note the S4 is a very useable everyday car, especially in practical Avant estate guise.
The 4.2-litre V8 model weighs in at a hefty 1660kg, enough to take the edge off what you'd expect a 344bhp compact saloon to be able to do in a straight line. The sprint to 60mph takes 5.4 seconds en route to an electronically limited 155mph, which makes it a little slower than Mercedes' astonishing C32 AMG and BMW's M3. That's not to say it lacks drama. The engine will rev to a heady 7,200rpm and the soundtrack alone is worth the price of admission. The engine does its best work between 1,100 and 5,000rpm, where the monstrous torque renders the six-speed manual gearbox almost superfluous. The gearchange is one of Audi's best efforts; smooth with a decent weight to the change linked to a heavy duty clutch, yet at any speed between 20mph and 120mph, it's tempting to just leave the S4 in fourth gear and hitch your surfboard to that huge swell of torque. Lazy? Maybe. Fun? Oh yes.
The S4 is a car that makes sense in such a wet country as ours. With all wheel-drive traction and a whole raft of electronic safety measures, it's effortlessly secure, offering less of the heart in mouth moments that often accompany a combination of big power, damp roads and an enthusiastic approach. That's not to say the S4 is a fuddy duddy that's forgotten how to entertain. Learn to drive the S4 properly and you'll be able to use more of that power more of the time than you ever thought possible. It's so addictive that only the realisation of quite how much Optimax unleaded you've burnt per session could possibly quell the temptation to repeat ad infinitum.
More of a rocket ship executive express than a racetrack emigre, a used Audi S4 is nevertheless a very desirable piece of automotive real estate. If getting from A to B via the squigglier bits on the map quickly and unobtrusively is what you desire, there's little that can touch it. The first of the post-1999 facelift 2.7-litre cars represent the best value at present although Audi have yet to build a poor S4. It may not be the most exciting choice available but if efficiency counts for anything, the S4 is a hands-down winner.