Buyers might be ditching petrol for diesel, but Audi is going against the grain with its new S6 and S7 – the fast four doors have always previously been petrol, but this latest generation opts for turbodiesel power instead (in Europe at least).
If betting everything on black sounds risky, it pays off brilliantly in practice. In fact, few four doors do everything quite so well – luxury, refinement, performance, efficiency, fun but secure handling… the S6 and S7 tick all those boxes, and unfashionable old diesel is key to the appeal.
The 3.0-litre TDI V6 is based on the same unit in the A6 50 TDI, and gets the same mild-hybrid system that helps store and redeploy otherwise wasted energy. It helps the S6 officially do 36.2mpg and 164g/km CO2, the S7 being just a smidge behind.
But there’s a twist in the form of an ‘electrically powered compressor’, or EPC, as seen on the SQ7 SUV. The EPC acts like a turbo but instead of spooling up on exhaust gasses it is – yes – electric and instant. In theory this takes care of very low-rpm performance to eliminate turbo lag, and means the S6/S7’s new, larger turbocharger doesn’t feel lazy when you’re trickling about. Add it all together and you get 344bhp, 700Nm (516lb ft) of torque and a 5.0-second 0-62mph sprint – less power than the previous-gen petrol S models, much more torque, and the ability to go full Tom Kristensen with over 620 miles between re-fills (if you’re good at lifting and coasting).
Power delivery isn’t quite the ballistic ball of any-gear/any-rev energy this leads you to expect, because somehow there is still lag, and you might wish for a petrol if you like winding revs right out because these turbodiesels feel a little flat when you do. But it’s the mid-range performance that’s so devastatingly effective. Really you’re only looking at a 2,000-3,500rpm window of opportunity, but the eight-speed auto keeps landing you back in the thick of it – second, third, fourth, fifth… it barely matters, the performance simply feels relentless.
At this point you might reasonably expect a ‘but it’s all ruined by sterile, understeery handling’ but it just isn’t. Quattro is awesomely sure-footed, but this chassis is superbly engaging and nimble too. Our test cars’ trick chassis surely helped, equipped as they were with optional rear-wheel steering and a sport rear differential. We also tried an S7 on the optional carbon-ceramic brakes that no-one will buy, but for the record that car’s point-to-point capability was downright ridiculous.
On German roads, optional air suspension felt noticeably floaty, where the regular coils and springs were firm and controlled if plenty compliant enough. So perhaps air will come in to its own on UK roads, but based on this drive we’d stick with the standard set-up.
The big decision, though, comes down to which of three body styles to choose: S6 Saloon (est. £60k) or S6 Avant (est. £62k), or the more stylish S7 Sportback four-door coupe (est. £68k). All are pretty fabulous, but for me nothing complements the do-it-all turbodiesel S concept better than the understated Audi S6 Avant.