Engineers, scientists and technicians at the world's automakers can build diesel engines that run as clean as their gasoline counterparts.
The challenge is to do it affordably.
Outfitting a vehicle with catalysts, particulate filter traps and other expensive, performance-strangling devices costs a lot of money, roughly $3,000 per vehicle, according to some suppliers. That's partially because of precious metals, such as platinum, that are used to cleanse the exhaust.
Diesels offer a fuel economy advantage of about 25 percent over gasoline engines, so in these days of radically unstable fuel prices, the pressure is on for automakers to boost fuel economy while keeping an eye on costs.
There is an affordable way to make a diesel engine run clean: urea injection. Periodically squirting urea into the exhaust system reduces harmful nitrides of oxygen, or NOx. The urea - a highly soluble liquid often used in fertilizers - breaks down into ammonia and reacts with the NOx in the exhaust system to produce harmless nitrogen and water vapor.
But Mercedes-Benz and Ford Motor Co., the two automakers that are leading the way in the development of urea injection, are trying to do the same thing in different ways. If they worked together on a common system, it would save them both money and speed diesels to the market.