The BMW 7 Series gets its latest and likely most fuel-efficient version in the 740Ld xDrive, a first-ever U.S. diesel version of the automaker's flagship sedan. Offered in one configuration — long wheelbase with all-wheel drive — the 740Ld xDrive will join more than a dozen other versions of the 7 Series when it goes on sale this spring. The automaker will show the diesel 7 Series at February's 2014 Chicago Auto Show.
BMW says the 740Ld xDrive starts at $83,425, including a $925 destination charge. That's $1,500 more than the gasoline-powered 740Li xDrive and just $30 more than the sole diesel version of Audi's all-wheel-drive flagship sedan, the A8 L 3.0 TDI ($83,395, including destination). If you pick the Audi, you can blow the difference on one of these. Standard and optional equipment lists are pending, but we expect that, like other versions of the 7 Series, optional equipment will send the 740Ld well into the six-figure range.How else do the cars stack up? The A8 TDI gets an EPA 24/36/28 mpg city/highway/combined. BMW has yet to tip its hand on EPA ratings for the 740Ld xDrive, but the automaker says other BMWs with the 740Ld's engine see 25 to 30 percent improvements in mileage versus their gasoline counterparts with similar engine displacement. The EPA rates the BMW 740Li xDrive at 22 mpg combined, so the 740Ld could see an EPA 28 or 29 mpg combined once the dust settles. That would trump BMW's ActiveHybrid 7 Series (25 mpg combined, $85,225 with destination) for the most fuel-efficient 7 Series.
But wait. Diesels always carry a caveat in the fuel's higher price. BMW requires midgrade 89-octane fuel in the gasoline 7 Series, and it recommends premium. A gallon of diesel runs 22 cents more than a gallon of premium, according to AAA; a year ago the difference was 27 cents. That blunts the efficiency advantages of diesel, but it's less drastic than if you shopped a diesel car against a counterpart that ran on regular gas.
Under the 740Ld xDrive's hood, BMW's 3.0-liter diesel six-cylinder engine makes 255 horsepower at 4,000 rpm but — typical of diesels and their sky-high compression ratios — a thundering 413 pounds-feet of torque from 1,500 to 3,000 rpm. That's just 67 pounds-feet short of the 750i's turbo V-8. With an eight-speed automatic transmission and BMW's xDrive all-wheel drive, the 740Ld xDrive hits 60 mph in 6.1 seconds. That's slower than the 740Li xDrive's 5.4 seconds but a few ticks ahead of the A8 L 3.0 TDI's 6.4 seconds, according to Audi.
Why are the two cars priced within spitting distance of each other? Perhaps because Audi fields the only U.S. competitor. Jaguar and Mercedes-Benz offer diesel versions of the XJ and S-Class, respectively, in other countries. Mercedes sold a diesel S350 BlueTec stateside in the last S-Class, but it remains to be seen whether the brand will reprise that with the sedan's redesign.
BMW also makes diesel versions of the 3 Series, 5 Series and X5. The automaker refreshed the 5-year-old 7 Series last year; gasoline versions of the 2014 model are on sale now.