Over the past several years, we’ve heard plenty about diesels — especially that they’re quieter, more civil, and smoke-free, and that they no longer bring a performance penalty. In Europe, though, there are quite a few models that bring better performance than their gasoline counterparts. Just a short drive in two high-performance, Euro-spec diesel sedans — a 2007 BMW 535d and a 2007 Audi A6 SE 3.0 TDI quattro — this past week was enough make our feelings about diesel a little warmer yet.
Both cars are part of a Bosch demonstration fleet primarily brought over to promote the current state of diesel technology to regulators, politicians, and non-profit groups in California.
The A6 has what we would venture to say is the quietest engine of any diesel we’ve driven yet, including the E-Class Bluetec. The 3.0-liter TDI V-6 makes 233 horsepower — almost as good as the 3.2-liter gasoline direct-injection V-6’s 255 hp — while peak torque stands at 332 lb-ft, compared to the gas A6’s 244 lb-ft. Even more remarkable, the TDI reaches peak torque at 1400 rpm, as opposed to 3250 rpm. With the six-speed Tiptronic, the A6 TDI can dash to 62 mph in 7.1 seconds and to a top speed of 153 miles per hour.
The first part of our route took us up a several-mile-long, six-percent highway grade where traffic moves at about 60 mph. It’s sent several test vehicles into convulsive hunting, as the transmission downshifts and upshifts repeatedly to maintain speed. But the A6 tackled it quietly in sixth gear, with plenty to spare thanks to the plentiful torque.
Then we came back for a spin in the 535d. It was equipped with an M Sport package, which includes sportier suspension tuning, flashier alloys, a racier-looking steering wheel, and sportier interior trim. There’s a 272-hp, 3.0-liter common-rail in-line six underhood, with a very impressive 413 lb-ft of torque. The diesel six far outpowers the 530i, which makes 255 hp and 220 lb-ft, and even exceeds the 360 lb-ft of torque made by the top 550i model’s 4.8-liter gas V-8. By the numbers, with the six-speed auto the 535d can get to 62 mph in only 6.5 seconds and to a top speed of 155 mph.
While the A6 impressed us with its quieter-than-gasoline, unobtrusive, and faster-than-perceived nature (it’s easy to lose track and speed), the 535d knocked our socks off. The six definitely has more of that old diesel character, with a strident clatter just off idle, but at the same time it feels like an old big-block V-8, roaring away from stoplights with a seductive burly sound that sounds a bit like an old M3 at full roar.
American buyers are used to diesel cars as being heavy and mushier than their gasoline counterparts, with dull responses. The 535d — especially with the M package here — runs counter to that stereotype, with a tight ride, quick steering, snappy shifts, and the same dynamic feel you get with BMW’s other sedans.
We intentionally kept the windows rolled down on both of these models, and never caught a whiff of smoke.
In a rather short, aggressive driving loop of just a few miles, we saw converted fuel-economy figures of about 24 miles per gallon on the A6 and, considering the even more stellar performance, 25 miles per gallon on the 5-Series.
Bring them on. They can’t come soon enough.--Bengt Halvorson
Emissions Noose Tightens for Automakers—TheCarConnection.com