2014 Audi A6 TDI. Click image to enlarge
With the introduction of Audi’s turbocharged direct injection 3.0L 24-valve V6 diesel engine in the mid-size A6 sedan this year, Audi joins a growing list of optimistic German automakers betting on increasing demand for diesel-powered luxury cars – not just SUVs – in North America. The rationale appears to be that luxury sedan buyers on this side of the Atlantic are now willing to sacrifice a little refinement (but not much) for better fuel economy along with the increased driving range and the abundant torque of a diesel engine.
The 3.0L V6 TDI diesel in the A6, also used in the Audi A7, A8, Q5, Q7 and VW Touareg, is certainly more subdued and refined than oil burners of the past. At idle, you’ll notice some engine clatter particularly if the windows are down. Under hard acceleration you’ll be aware of a distant thrashing sound, though it’s smartly subdued by generous sound insulation. But in everyday driving around town and cruising on the freeway, the TDI diesel engine is barely audible. During the week that I drove the A6 TDI, there were many times when I forgot there was a diesel engine under the hood.
With 70 fewer ponies than the A6’s available supercharged 310 hp 3.0L V6 gas engine, you might expect the 240 horse diesel engine to offer inferior acceleration. Not so. With an additional 81 foot-pounds of torque – a massive 406 lb-ft from just 1,750 – 2,250 rpm – the A6 TDI takes just 5.7 seconds to sprint from 0 to 100 km/h, only 0.2 seconds slower than the supercharged A6 3.0, according to Audi. And typical of a diesel, throttle responsiveness at low revs means you don’t have to wait for forward momentum to build up – the torque is there right away. Just put your foot down and hold on! I scared at least one passenger that way!!
(Just for the record, the A6’s other available engine, a turbocharged 2.0L four-cylinder makes 220 hp at 4,450 – 6,000 rpm and 258 lb-ft at 1,500 – 4,300 rpm.)
When it comes to fuel economy, the 2014 A6 TDI is the wealthy miser’s friend with EPA ratings of 9.8 city/6.2 highway/8.1 combined, much better than either the supercharged 3.0L V6 sedan (13.1 city/8.7 hwy/10.7 combined) or the turbocharged 2.0L four-cylinder A6 sedan (11.8 city/8.1 hwy/10.2 combined.)
2014 Audi A6 TDI engine bay, dashboard. Click image to enlarge
With over 12,000 km on the clock of our A6 TDI test car, the trip computer was showing average long-term fuel consumption of 8.3 L/100 km, very close to the official EPA rating of 8.1 L/100 km. The A6 TDI’s freeway fuel economy is enhanced by the tall highway gearing of its ZF eight-speed automatic transmission; the engine turns over just 1,300 rpm at 100 km/h. As well, fuel economy in city driving is reduced by approximately 0.4 L/100 km due to the A6 TDI’s automatic stop-start system which stops and starts the engine at stop signs and traffic lights. For the most part, I found this to be a smooth transition, apart from the sound of the engine starting up. But if you don’t like it, there is a button to deactivate it. As well, a driver-selectable Eco mode is there to tame the engine and transmission’s performance a bit for improved fuel economy.
As with its competitor’s diesel engines, the A6 TDI’s engine requires a urea additive called AdBlue at certain mileage intervals in order to keep exhaust emissions within allowable limits. This is usually added during servicing under warranty and at regular service intervals after that.