Clean Diesel Audi Gets 42 MPG

Eight states, the nation's capital, 1,039 miles, and just 24.7 gallons of fuel - that was the tally after the first stage of the Audi Mileage Marathon that Green Car just completed. If you haven't already done the math, that works out to nearly 42 miles per gallon of combined city/highway driving. And let us emphasize the city driving...our route included time consuming and fuel robbing stints from Central Park in New York City to Philadelphia, Washington DC, Cleveland, Toledo, and rush hour Chicago.

That's truly impressive fuel economy by any measure, but the car we were driving wasn't a tiny economy model or the latest generation hybrid with solar panels on the roof. Those numbers were achieved behind the wheel of a 3,725 pound, all-wheel-drive, five-passenger luxury performance sedan. Our ride: The Audi A4 quattro powered by the remarkable 3.0 liter 50-state legal TDI clean diesel V-6.

The 3.0 liter TDI is scheduled to come to the United States first in the seven-passenger Q7 SUV. Its advanced, second-generation common rail direct injection TDI technology features 1,650 bar (23,931 psi) piezo injectors with eight-hole nozzles and an intercooled VTG turbocharger. Peak torque is delivered from 1,500 to 3,000 rpm, providing a satisfying kick in the back. Audi rates the European A4's 3.0 TDI power output at 369 lbs-ft of torque and 240 horsepower. The U.S version of the 3.0 TDI slated for the Q7 will offer 225 horsepower and 405 lbs-ft of torque.

Audi pegs the A4's 0-60 mph time at a quick 5.7 seconds with a top speed of 130 mph. The 3.0 TDI's power is efficiently transferred to ground via a six-speed Tiptronic DSP transmission with sport programming and Audi's renowned quattro all-wheel-drive system. We drove through heavy rain on the third day of the competition leaving Cleveland and the quattro system kept the A4 well planted with reassuring grip.

The A4 TDI was loaded down with two well-fed passengers, a marathon's worth of luggage, cameras, computers, a wireless Wi-Fi hot spot, fuel, and a hefty data-logging computer mounted in the trunk to track and record our every move, bringing the gross vehicle weight to well over 4,500 pounds. On the second day of driving, a route that took us from Washington DC to Cleveland, Ohio over the rolling mountains in Pennsylvania, our car averaged a class high of 44.2 mpg for the day.

Though we didn't go to hypermiling extremes, the Audi Mileage Marathon was a competition among journalists and bloggers, so our driving style was geared toward maximum efficiency. Many of the drivers in the Mileage Marathon tucked in behind semi trucks to gain an aerodynamic advantage, but we found that driving conservatively was the best overall strategy. The 3.0 TDI's power curve flattens out with maximum torque beginning at 1,500 rpm, so short shifting and cruising at the low end of peak torque seemed to work best. Besides, driving for hours on end locked to the bumper of a semi simply isn't much fun (and can be dangerous), plus you miss all the spectacular scenery along the route.

Our car for the Audi Mileage Marathon was decked out in Michelin colors with a big Bibendum (aka the Michelin Man) on the hood ... clearly the best-looking car in the fleet. We were fortunate to be partnered with Bob Massa as co-pilot for the entire wave. After 38 years with Michelin, Massa shared a wealth of knowledge about tires in general and the fuel-efficient Green X tires fitted to the Mileage Marathon cars in particular.

Michelin's new Latitude Tour HP Green X tires were mounted on all the Q7 and Q5s while the A4s and A3s featured Michelin's Primacy HP Green X low rolling resistance tires. Green Car is planning a more in-depth look at greener, more efficient tire technology in the near future.

Ending in Los Angeles on October 20, the Audi Mileage Marathon is a very ambitious 4,800-mile transcontinental journey that zigs-and-zags to major markets from New York to the West Coast. With a total of 23 A3, A4, Q5, and Q7 models competing and at least as many clean TDI Audis along with executives, staff, and support personal, the Marathon is an extraordinary undertaking with the mission of spreading the word about the new generation of clean diesel technology. The big seven passenger Q7s are regularly delivering over 30 mpg on the trip. Our experience with the powerful and fun-to-drive A4 averaging nearly 42 mpg speaks volumes about the potential of clean diesel as one of the primary solutions moving forward.