It’s interesting how the success of diesel internationally, hasn’t translated into success here in North America. We borrowed the BMW 535d and the Audi A6 TDI for a direct comparison, but also to find out whether or not their diesel powertrains can deliver a real luxury experience.
The gasoline versions of these luxury sport sedans helped build a reputation of graceful, yet fiery road manners. Will the substitutions of diesel power tarnish that luster or will it provide tangible reasons to make the switch?
Under the hood of the BMW 535d is a turbocharged 3.0-liter inline-six engine making 255 horsepower and 413 lb-ft. of torque. Thanks to BMW’s xDrive system, all four wheels are as active as an angry volcano, erupting to send that asphalt-ripping torque to the road in a surprising manner.
The diesel 5 Series can hit 60 mph in 5.7 seconds, just a few tenths of a second slower than the non-diesel model. Despite its quickness, the diesel Bimmer is quite fuel conscious thanks to its eight-speed automatic transmission, helping it earn 26 mpg in the city, 37 mpg on the highway and 30 mpg combined. Over the course of a week loan, the car returned exactly the 30 mpg average it is advertised to.
Audi’s turbocharged 3.0-liter V6 engine makes 240 horsepower and 428 lb-ft of torque, meaning it has slightly less horsepower and more torque. The A6 is also lighter, a fact that helps it get to 60 mph two-tenths of a second faster than the 535d. That’s hardly a noticeable difference, but bragging rights are still bragging rights. It’s fair to say both of these cars are more performance-oriented diesels, as opposed to the humbly outfitted, and fuel-sipping Mercedes E250 BlueTEC.
The specification stalemate continues with the A6’s transmission with an eight-speed that helps the quattro-equipped A6 get 24 mpg in the city 38 mpg on the highway and a combined rating of 29 mpg. Real world fuel usage in the A6 is as advertised, lagging just behind the BMW. If fuel economy is what you’re after, the BMW is more efficient than any gas version of these two cars.
Both look quite stylish and peaceful despite the earthquake-inducing engines tucked under their hoods. The executive sport-sedan look is present thanks to LED lights, 18-inch wheels, and chrome bits. As part of the Prestige package, the A6 features the S-line exterior trimmings, including imposing 20-inch wheels. In the end it’s the A6 that ends up looking a bit more intimidating on the road.
The 535d starts at just $57,525, or just $1,500 more than a gas-powered 535i. Our all-wheel drive tester sports a number of other packages including a heads-up display, driver assistance technology and rear seat warmers and rings in at $73,600. The diesel powered A6 starts at $58,395, which is $2,400 more than the 3.0-liter TFSI gasoline engine. Fully loaded, our A6 TDI costs $76,500.
Inside, the two cars do everything to let you know that you’re in a luxury vehicle. The BMW is a sexy mocha colored nappa leather showcase with seats that are extremely comfortable, supportive and infinitely adjustable.
However when it comes to the interior, it’s the Audi that leaves the lasting impression. While the black leather seats don’t coddle you as well as the BMW’s, the interior accents and layout is far superior. The pin-striped accents must be styled after Audi CEO Rupert Stadler’s corporate outfit and feel oh-so-executive-class. After seeing the A6’s modern interior, the BMW’s color-scheme seemed a bit Western-themed.
If there’s one drawback with the Audi, it’s that it has less rear seat headroom and a smaller trunk than BMW’s offering. Both cars feature extravagant niceties that bring the price point past $70,000. Heads-up display, blind-spot assistance, adaptive cruise control and heated seats are all here. But the $5,900 Bang and Olufsen sound system is probably the hardest premium add-on to justify.
As much as the Audi’s interior shouts MBA, the engine screams NVH – that’s noise, vibration and harshness. Upon cold start up, the A6 greets drivers with a jittery idle and the unmistakable clacking soundtrack of a diesel, which is impossible to hide from. The four-ringed sedan vibrates with such intensity that you can almost mistake it for a massaging seat feature, with the only relief coming from turning the whole car off. Downshifts send a shiver throughout the vehicle and while the A6 has an enjoyable and responsive steering feel and throttle, we can’t help but think that the diesel engine doesn’t suit the car as well as the supercharged gasoline V6 does.[vs-comparsion-table]
In the BMW, things are decidedly less jarring. The diesel inline-six is properly muted and impossible to hear from within the cabin. The engine is virtually lag-free and throttle response is just what you’d expect from a car with the BMW badge on the hood. An excessive amount of torque is present in both vehicles, allowing highway merges with ease, but the BMW’s extra horsepower is put to good use during passes on the freeway. The chassis is tight, with perhaps overly heavy steering emerging as a small complaint. Put the car in Sport plus, or turn off the traction control, and the rear-biased all-wheel drive system allows you to have a bit of fun sliding about.
Both cars maintain a fun-to-drive demeanor with tight handling and solid power. Fortunately the sport-sedan feel is present and enhanced in each car as they sprint off the line with enthusiasm. They also offer impressive fuel economy, especially for their size and cylinder count. However, while diesel powered Audis have seen success in countless endurance races, the expectations are a bit different in the world of passenger vehicles, where refinement and NVH are top priorities.
This is where the 535d excels. It stands out as a diesel powered car, which is refined enough for a luxury marque. If the choice was between diesel power and the four or six-cylinder gasoline powered 5 Series, the 535d is the model to take.