Diesel's Greener Bill of HealthQuick, think diesel. You might picture 18-wheeler semi-trucks, Vin (the actor) and reams of black smoke. But how about green? Sans the grime and cold weather choking remembered from the '70s, modern-day diesel boasts benefits that make it a viable contender for an eco medal. In Europe, where gasoline is even pricier than it is here, diesels account for up to half of all passenger cars, according to the Diesel Technology Forum. Increasingly, American buyers are catching on to technology advancements that have alleviated the messy diesel headaches and difficult cold winter ignitions of yesteryear. (See "Diesel Developments.")

In addition to reduced emissions, today's diesel fuel also takes less energy to produce and costs consumers less in federal taxes than its gasoline counterpart, so diesel owners can save a little money while they're helping to save the environment. Diesels' increased availability has opened the door for even "greener" fuel — biodiesel. Biodiesels range in their content and dependence on natural resources, from ethanol and petroleum blends to corn oil and recycled fast-food vegetable oil. Below are the stories of women who are willing to make diesel — both regular and biodiesel — their first choice.

Cleaning Up Their Act Libby Manly of Durham, North Carolina, bought a blue 2006 Volkswagen Golf TDI in August after transferring jobs from Boston, where she didn't own a car. Manly averages 45 miles per gallon.

"I wanted to get something that was fuel-efficient and not so reliant on petroleum," she said. "I was looking at hybrids and test-drove a Prius and an Insight. I felt that they were too gadgety for me. I didn't like the way they looked. They were too 'space age' for me."

Other diesel owners chose their cars to work with a lower budget.

Susan Beck of Belvedere, Illinois, was compelled by diesels' fuel-efficiency. She originally wanted to buy a gasoline-powered Jeep Liberty before she moved from Milwaukee to Illinois with her 2-year-old son, but she feared fuel costs would be high with a gasoline engine.

"I knew the diesel got much better fuel economy," she said. "I asked about it at an auto show in Milwaukee. I couldn't justify [the gas-powered version] when I was driving a 100 miles a day," she said.

Beck purchased her Jeep Liberty CRD in March and averages 25 to 27 miles per gallon. But her switch to diesel hasn't been painless. She's already had to replace the EGR valve twice, at 5,000 miles and 12,000 miles.

"In Wisconsin they had 'premier' diesel, but so far in Illinois we haven't found it, so we've been putting in additives," she said. "Each time it was out of service for three days. You have to have a diesel tech on staff. They're running codes and checking things and getting input from Chrysler engineering. We're wondering if the not-so-good grade of fuel is gunking up the valve."