Ward’s 10 Best Engines competition has recognized outstanding powertrain development for 20 years. This installment of the 2014 Behind the 10 Best Engines series highlights development of BMW’s 3.0L turbodiesel I-6 used in the 535d.

Diesel engines still suffer from a negative image among many U.S. consumers, who – from past bad experience or hearsay – incorrectly view them as poky, smoky and noisy.

But modern compression-ignition engines own more than half of the European market and are fast gaining popularity elsewhere, including here. This is largely due to European tax policies that make diesel fuel cheaper than gasoline, and also due to their general excellence these days.

As we know, diesels enjoy the advantages of higher torque for stronger acceleration and significantly better fuel efficiency compared with similar-size gasoline engines. But their drawbacks are higher engine cost and (in the U.S.) higher fuel prices and spotty availability. There's also the oily fuel itself, which is much cleaner today but still better to keep off your hands when refueling.

That said, today's advanced diesels are simply too good to ignore, so WardsAuto editors tested six of them (more than ever before) and awarded half of those 2014 10 Best Engines trophies. And this smooth, quiet, powerful BMW turbodiesel inline-6 may be the best yet.

After testing it in a ’14 BMW 535d sedan, they called it “remarkable,” “stealthy fast,” “responsive,” “a blast to drive” and “arguably...the all-around quietest diesel we've even driven.” This despite the new N57 I-6 losing 10 hp and 12 lb.-ft. (16 Nm) of torque compared with the previous-generation Ward's 10 Best Engines award-winning (2009 and 2010) I-6 diesel it replaces.

It also uses a single variable-geometry turbocharger instead of the previous twin turbos and less expensive solenoid-type fuel injectors in place of piezo-electrics.

But the most important difference is substantially better EPA fuel-economy ratings at 26/38 mpg (9.0-6.1 L/100 km) city/highway in the ’14 535d vs. the earlier engine's 23/36 mpg (10.2-6.5 L/100 km) in the slightly smaller previous-generation 535d.

In real-world Detroit-area driving, WardsAuto editors topped 35 mpg (6.7 L/100km), better than some 4-cyl. diesels and gas-electric luxury hybrids tested. They also found its improved stop-start system smoother and faster to respond than before.

Through an exchange of emails, BMW diesel engine development chief Peter Nefischer highlights the N57's top design priorities.

“Efficiency, low emissions and the best possible power-to-weight ratio were the key objectives,” he says. “Also, a compact package was very important in terms of total vehicle architecture.”