Day 6: Jiayuguan to Lanzhou, 466 miles
We visit the fortress at Jiayuguan, built in 1372 at the western end of the Great Wall. For a long time, it was the only safe refuge for traders on the Silk Road. Up to 30,000 soldiers were once garrisoned at the huge complex, which was partially destroyed during the rampages of the Red Guard. Only eroded remnants of the Great Wall remain standing outside the fortress. We come across one section that shows the ravages of both time and looting for building material. A lone shepherd wanders over to find out what this group of cars portends, and silently suffers our clicking cameras and mutely refuses any offer of compensation for his posing. His quiet gravitas touches us with an almost spiritual caress.

We reach Lanzhou at dusk in a crush of rush-hour traffic. The former garrison town, now the capital of Gansu Province, houses more than a million people and sprawls on both sides of the Huang He, or Yellow River. I can't believe the drive is ending and wish I could stay on for the final leg into Beijing. I give car 11 a final, affectionate pat and silently thank it for safely ushering me from the modern world into history and back again. I clasp the hand of my co-driver a final time, gather my bags and walk away from one of the finest automotive adventures of my life.

When most Americans think of diesel cars, they think of either large trucks or slow rattling sedans belching black smoke. Europeans have a much different view of diesel; they see huge fuel efficiency gains, mountains of low-end torque and engines that last for hundreds of thousands of miles.

Americans may soon share the same view thanks in part to a combined effort from Mercedes-Benz, Audi and Volkswagen. In the past, particulate and nitrogen oxide (NOx) emissions kept diesels from being considered a realistic alternative to gasoline-powered cars. Mercedes-Benz Bluetec engines use two different filters in combination with urea injection to eliminate the problems normally associated with diesel fuel. The first filter traps NOx and converts it to water and nitrogen, while a second filter traps particulate matter responsible for the characteristic diesel soot.

The ability for all this to work in America hinges on the United States adopting low-sulfur diesel and the government approving emissions systems equipped with a component that would involve urea consumables, like Bluetec. If these things fall into place, we may all be driving 40-mpg diesel cars-without having to install an electric motor.

By Greg N. Brown
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