2009 Audi Q7 TDI Premium quattro Tiptronic

Full-sized SUV with a green footprint

By Nina Russin

2009 Audi Q7 TDI

Which technology is greener: gasoline-electric hybrids or clean diesel? Engineers on both sides of the fence can make good arguments in their favor. Hybrids yield exceptional fuel economy in stop-and-go traffic, whereas the fuel economy gains for diesel cars are smaller, but more consistent across-the-board.

Over the long term, owners of hybrids must address the issue of battery life and disposal: a problem that doesn’t exist for diesel. On the other hand, gasoline is still more readily available than diesel in the US, and in many cases, costs less.

Traditionally, American drivers have shunned diesel technology, primarily because of bad experiences with vehicles built several decades back. I can’t emphasize enough how different the current generation of diesel cars are from their predecessors. A relatively recent technology known as common-rail diesel uses on-board computer controls and very high fuel-line pressures to give the new cars power and performance comparable to gasoline cars.

The new clean diesel cars have excellent throttle response, and vastly reduced diesel tick. Audi has reduced particulates out the exhaust by 98 percent, compared to cars built in the late 1980s. Torque is up 70 percent. In short, the cars are environmentally friendly, fun to drive, and remarkably fuel-efficient. Read the rest of this entry »