Audi S4 Avant TDI driven: turbodiesel sports-wagon tested

Yum, a new Audi S4. A classic ‘all the car you’ll ever need’.

Always has been. The S4 is one of the world’s last Q cars. Subtle looks, but enough punch to see off a Cayman. Big space, with neat’n’tidy handling. Lots of pace, in all weathers. 

It’s never the first car you park in the Dream Garage, but even if you had an underground bunker brimmed with Bugattis and Paganis, you’d use an S4 more days than a platinum-plated Lambo-segg.

And now it’s powered by diesel fuel?

Indeed. Seems a weird move, doesn’t it? Audi was caught just as red-handed as its Volkswagen parent in the dieselgate emissions-dodging scandal of 2015 and beyond. The UK has responded by shunning diesel cars faster than evicted Love Island contestants. So far in 2019, diesel’s share here has shrunk by almost 20 per cent, compared to 2018. And it tanked in 2018 too…

So, why is Audi still banging the diesel drum?

Because it sees a future in cars that have deep reserves of torque to punt them along, and emit less CO2 than a car with a petrol habit, while travelling further on a tank. Torque is much more useful in The Real World than peaky top-end power. Especially in a roomy family wagon. Sounds familiar? They’re the reasons that Europe fell painfully in love with TDIs in the first place. And still quite compelling, if you're not a knee-jerk politician.

It’s efficient then?

Officially, it’ll do 39.8mpg and emit 166g/km of CO2 on the new WLTP testing cycle. 

Is that it? Hardly box office stats. 

On the old testing regime, any diesel that sunk below 50mpg would’ve been a laughing stock., but the latest lab tests are supposed to be more realistic. As a result, you’ll stand a healthy chance of not just matching what Audi’s website claims, but beating it. 

Our S4 Avant test car was regularly claiming over 40mpg. The old petrol V6 rarely climbed above 30 to the gallon. Job done.

Bet it sounds pants. 

It doesn’t sound like much at all, really. There’s a vaguely six-pot rumble in the middle distance when you clog it. It sounds more expensive than a four-cylinder diesel by a mile, but hardly justifies brandishing four polished tailpipes.

Then again, the old petrol V6 was hardly a vocal event. At times, it was even a bit droney, in Dynamic mode. A tad artificial, like it was singing through autotune. So forget the noise argument. You’re missing out on negligible entertainment, and going another couple of hundred miles on a tank.

Bet it understeers with that anchor behind the grille.

It’s more leaden on turn-in than it used to be. Ironic, really – when the old S4 was launched Audi bragged that the new engine saved 14kg of front-axle weight. Whoops. 

But, that’s been compensated for by a simply biblical wallop of torque. In the old car, you got 369lb ft and that felt like a lot. In the new S4, you’ve got 516lb ft. That’s more than a McLaren 600LT churns out. 

So what? It’s quattro-drive. Audi-speak for understeerzzzzzzz…

Not this time. The S4’s sport differential, which claims to shuffle torque to the wheel that can best deploy it, has been awakening in the S4 TDI. Before now, the car was so tractable it was impossible to feel the diff doing its thing. But now it’s got to deal out a volcano of torque, there’s a sense that the rear wheels are powering the car out of a corner, as the body hunkers down. It’s really punchy, and feels agile on the throttle. Like a smaller, wieldier SQ7 in fact – which is one of Top Gear’s favourite fast big SUVs.  

Is it actually quick?

Quick enough. On paper, it’s got 342bhp – a couple of nags down from the petrol-swigging S4. On the clock, it does 0-62mph in 4.9 seconds – identical to the petrol version. The top speed remains pegged at 155mph. 

Does it feel as quick? No. But that’s not the engine’s fault – it’s aided by electric anti-lag turbo technology powered by a 48-volt mild-hybrid battery system. At speed the S4 can coast engine-off for up to 40 seconds. Meanwhile, stop-start engine response is instant and the turbo’s rarely caught napping. What lets the side down most is the eight-speed automatic gearbox. 

Audi – like the whole VW Group, and other manufacturers besides – has really struggled to make its once-peerless autos behave when shifting on a new WLTP-friendly strategy. It’s swift enough on the paddles, but the automatic mode is bizarre. Too keen to shift to high gears early on, it slurs the kickdown, and selects second or even first gears for mild prods of the throttle. What’s the point in having eight speeds and all that torque if the gearbox thinks it’s connected to a food blender?

Anything else?

The rest of the S4 is what we liked heartily before. The boot’s huge, it’s comfortable, the interior is plush and sophisticated, though we’d swap the new touchscreen for the old clickwheel-mit-buttons set-up in a heartbeat. The new honeycomb-mesh grille looks tidy too – sporty, but not at the expensive of the S4’s stealth. 

Shifting the S4 to diesel has also done Audi a favour – it’s put some daylight it between it and the petrol V6 RS4, which has struggled to come across as more than an S4-plus.

7/10

3.0-litre turbodiesel V6, 342bhp, 516lb ft
39.8mpg, 166g/km
0-62mph in 4.9sec, 155mph
1825kg
£49,000 approx