Audi A4 TDIe Clean Diesel Bests Prius at Combined 51 MPG

The new Audi A4 2.0 TDIe recently introduced in Europe is the latest model to earn the ‘TDIe’ designation – Audi-speak for the addition of fuel saving measures above and beyond the standard clean diesel TDI. With a new 134 horsepower variant of the 2.0-liter diesel engine first shown in the A6 2.0 TDIe, the A4 2.0 TDIe improves upon the 40 to 48 mpg achieved by the rest of the A4 2.0 TDI lineup to earn a combined 51 mpg.

Key to the efficiency improvement is a start-stop system that cuts engine power at idle when neutral is selected and the clutch is released (a six-speed manual is the only available transmission). The system restarts the engine in two-tenths of a second when the clutch is depressed. Audi claims the system is good for about a four percent improvement in fuel economy. A regenerative braking system stores wasted kinetic energy in the vehicle battery to reduce engine load and further reduce fuel consumption.

That little ‘e’ in the title also means lots of other smaller efficiency improvements, including a higher transmission final drive ratio, a power steering pump that operates only on demand, and low rolling resistance tires. The A4 TDIe also cuts fuel consumption by reducing drag with a streamlining underbody panel, an extra enclosure on the grill, and sport suspension settings that drop ride height by eight tenths of an inch.

Despite the performance potential of that sport suspension and a 143 mph top speed, an efficiency-focused version of the Driver Information System in the instrument cluster aims to improve fuel economy by keeping driving style in check. The system, included in other TDI models as well, recommends gear shift points and uses sensor analysis of driving conditions and styles to give specific driver advice. Audi says the system has been proven to increase fuel economy by as much as 30 percent.

While there are no announced plans for the TDIe lineup to make an appearance on American roads, Audi is currently testing the waters here by introducing a TDI version of the Q7 SUV in the fall of this year, followed by an A3 TDI in 2010. This American diesel rollout comes in tandem with a clean diesel ad campaign aimed at overcoming historical diesel stigmas. Should the U.S. market be receptive, there is clearly great product at the ready.