V8 Audi S4: 9 Things To Know Before You Buy

While it might not be quite as sharpest sports saloon of the mid-2000s, the B6/B7-generation S4 is a thoroughly appealing car. It packages V8 poke and a capable all-wheel drive system in a handsome saloon body, with an ‘Avant’ estate version available should you be wanting for more space.

With prices starting at just £5000 (budget £7000 upwards for a tidy model with reasonable mileage), you can’t help but be tempted. But there’s plenty of things - both good and bad - you need to know before taking the plunge. We chatted to 2006 B7 S4 owner Chris Gregory to get a sense of what it’s like to own one, and Hassan Fazel of Manchester-based VAG tuning specialists Awesome GTI for an expert view. We also got behind the wheel of Chris’ car, to get an idea of the driving experience.

Here’s what we learned:

The chassis is capable, but not thrilling

Stepping from a modern performance car straight into a 10-year-old one usually results in the latter machine feeling soggy. That’s not the case with this S4, where you’ll find a very stiff setup. It rolls a lot less than I expected it to, although the trade-off is a particularly brittle low-speed ride.

It’s no thriller in the corners, though: the quattro all-wheel drive system runs a 60/40 split (B6s are split 50:50 - one of the few non-cosmetic differences), biasing the rear wheels only slightly. As a result, it’s rarely anything other than utterly neutral during hard cornering. Push too far, and you’re in understeer territory. The steering meanwhile is slower than the ultra-quick racks we’ve gotten used to, but it does feel more natural than a lot of more recent fast cars from Audi.

The engine dominates the driving experience

The less-than-thrilling chassis is perfectly forgiveable, as the engine is an absolute peach. Yes, the 339bhp, 302lb ft unit does have to haul around 1700kg of car, meaning that the S4 never feels that quick, but you just don’t care. Why? Because it’s an utter joy to row through the gears with this 4.2-litre lump.

It’s smooth, lazy and rumbly, and is the centre point of the driving experience. It’s no wonder the current V6 turbo S4 and S5s are a little underwhelming by comparison: the engine is the main selling point with a car like this. Factor in the reasonably slick six-speed manual - fitted as standard - and you’ve a match made in heaven. It’s a wonderful thing to cruise round in, and Chris is certain that the manual is the one to have. “It makes it a different car. It’s a lot nicer to drive - I test drove both [manual and auto] before buying,” he says.

You might be disappointed by the comfort

Even at 10 or so years of age, the interior of this particular B7 still looks and feels great, if a little tired around the edges. But it might not be quite the comfy cruiser you’re expecting, and not just because of the firm ride. The problem lies with the seats. “They might be Recaros, but they’re not that comfy. It’s a bit of a let-down, really,” owner Chris tells us.

It's horribly expensive to change the timing chain tensioners

When it comes to buying one of these cars, Awesome GTI’s Hassan Fazel has two main pieces of advice: make sure it’s been serviced at the proper intervals, and check carefully for excessive timing chain rattling on a cold start.

“If oil servicing has not been done, oil galleys can get blocked and this can cause issues to the timing chains,” he said. Once the tensioners start to slack, you could end up with a misfire and a check engine light for your troubles.

If the chain and tensioners do have to be changed, you’re in for a world of financial pain. The parts themselves are only “a few hundred pounds,” but for everything to be fitted, the engine has to come out, giving you a bill that will run into the thousands.

It’s something to bear in mind if you’re looking at an S4 that’s done over 100,000 miles. Want to prolong the life of the chain? Keep up with the oil changes, and make sure it’s the right oil ( 0w40 or 5w40). Waiting until it’s warm before you thrash it is going to help too, but hopefully you already know that.

The only real downside to the V8 - possible timing chain woes aside - is that it’s rather muted. “It’s not as loud as I would have wanted,” Chris says, before conceding, “but then it is civilised.”

Unsurprisingly, he’s thinking about doing something to up the volume a bit, and so do a lot of owners: Hassan notes that the most popular mods from its B6 and B7 S4 customers concern the exhaust.

There are several options. You could go for a full system from a firm like Milltek, or for something more cost effective, a cat-back system with a high-flow catalytic converter will give you plenty of volume and be kinder on the wallet. Meanwhile, there are firms out there that will modify the existing pipework. For example, PCW Exhaust Mods - whose work we’ve seen before - will “reconfigure the internal layout” of the back boxes for around £260 (and also remove the resonators, if you want to take it further) leaving you with a stock-look system that belts out a much more pleasing soundtrack.

You'll probably want to concentrate on suspension mods

Aside from exhaust systems, it’s not worth spending much modifying the engine. Hassan tells us the standard air box is “pretty good,” so what most “tend to do is put a high-flow panel filter in” from a firm like Pipercross or K&N, and little else.

Meanwhile, we’re told “yes you can remap these, but gains are not massive - you’ll get 10-15bhp at the most.” So it’s not something to put high on the priority list, although Hassan notes that you will see a noticeable improvement in throttle response. Want much more power than 339bhp? You’re probably going to want to up the budget by quite a bit and go for an RS4.

Otherwise, pay more attention to the suspension. With the age of these cars and the mileage many have reached, it’s going to be pretty tired down there. A control arm refresh kit from 034Motorsport (which uses stiffer, more durable rubber) can be bought for just over £450, and while that’s going to work out quite pricey once you’ve factored in fitting, it’ll give you sharper handling and eradicate any slop in the steering. You may also want to swap the stock dampers for a new set of coilovers.

Servicing costs are reasonable

You could save yourself money by servicing the S4 yourself, but even if you’d rather not, you might find it to be cheaper than you’d expect to get sorted at a specialist. Awesome GTI charges £200 for an interim service and £350 for a full service, while a little further down south at MRC Tuning you’re looking at £282 or £454 for an interim or full.

But fuel economy isn't

“I knew the fuel economy would be bad, and it is, really,” Chris tells us, adding, “I don’t think you could ever prepare yourself for it.” He averages 20mpg, but on a spirited drive, it does around 10mpg. “I’ve seen 8mpg before,” he notes, but on the other side of the coin, Chris has managed 35mpg on a long, very gentle run.

There are other things to look out for

While a good service record and a healthy chain are the main things you need to be wary of, there are other things to keep in mind. If you’re buying an automatic, it’s worth getting the gearbox oil changed immediately as “the chances are it hasn’t been done,” Hassan says. “Trying to source a second-hand ‘box for one of these is very, very difficult,” he warns. It’s a good idea to get the rear differential oil changed, too.

Finally, make sure the air conditioning of your prospective S4 is working, as broken condensers are a common complaint and aren’t cheap to fix.

Are you tempted to go for a B7 Audi S4? Or do you own one already? Let us know in the comments!