After a promising start, the diesel's fortunes sputtered. Today its future is bright — and clean."You drive a what?"

"A diesel."

"A diesel?"

That's the response I usually get, along with a look of incredulity, when I tell friends that I drive a VW Golf TDI (turbodiesel direct injection).

It's not that they're accustomed to seeing diesels only at truck stops. It's that they expect me, an eco-conscious citizen bent on living a more sustainable lifestyle, to be driving something different. I then spend the next five minutes explaining that instead of driving a slow, loud, smoke-belching beast like they remember from the '70s, I drive a sleek, quiet speedster that runs on biodiesel and used vegetable oil and is as easy on my wallet as it is on the environment.

Yes, the diesel engine has come a long way from its bulky beginnings in the early 1900s. While its automotive future faltered toward the end of the 20th century here in the U.S., it is presently experiencing a resurgence of sorts. Still the darling of the trucking industry the world over, the diesel engine's strength, reliability, efficiency and ability to run on alternative fuel, coupled with the EPA's new National Clean Diesel Campaign, has car buyers reconsidering diesels as their future mode of transportation.

So what's changed, you ask? Let's take a look.

Peanuts Dr. Rudolph Diesel (1858-1913) unveiled his compression engine at the 1898 Exhibition Fair in Paris. There, amid the grandeur of the world's fair, the talk was not only of the engine's impressive 75-percent efficiency rating (compared to the steam engine's 12 percent and the gasoline engine's 25 percent), but of the fact that it ran on plain old peanut oil.

Unlike the gasoline engine, which runs on combustion (gas is pumped into the pistons and ignited by a spark), Diesel's engine ran on compression (air is compressed to the point where it becomes extremely hot, thereby igniting the fuel mixture when it is injected). The result was an engine that was stronger, simpler and more efficient.

Seems that besides being a genius, Diesel was a bit of a socialist as well. It was his hope that by fueling an engine with biomass (plant material, vegetation or agricultural waste), he could take the power away from big industry and put it back into the hands of the everyday farmer and small businessman. "The use of vegetable oils may seem insignificant today, but such oils may become in the course of time as important as petroleum and the coal tar products of the present time," he said in 1912.

Diesel decided to travel abroad and share his engine design (including its uses in submarines and naval ships) with the Queen's navy. Unfortunately, while crossing the English Channel, he disappeared over the side of the ferry and was never heard from again. Conspiracy theories abound as to who or what caused his disappearance.