endary reliability, longevity, efficiency and performance. In Europe, where fuel costs roughly twice what it does here, diesel engines power more than half of all passenger vehicles.

But they remain an almost insignificant factor here. Part of this is due to a reputation for being noisy and smelly and stupid attempts to convert gasoline engines to diesels. But it is mostly due to relatively cheap fuel in general and no price break for diesel fuel in particular.

The noisy and smelly part is now pretty much history, with the newest generation of diesels, and fuel prices are climbing at a scary rate. Hopefully, regulators will soon realize that taxing diesel at such an exorbitant rate is going to hurt in the long run.

One thing regulators have done is force oil companies to produce and make available cleaner diesel fuel. The huge amounts of sulphur in fuel has a nasty corrosive effect on emission-control equipment -- as well as our lungs. But as of this fall, cleaner diesel fuel will be available across North America, encouraging the introduction of a new generation of clean diesels.

Some of the most interesting and promising of these will come from Mercedes-Benz, which has a long history of diesel engine prowess dating back to 1936 when it became the first manufacturer to offer a diesel-powered passenger vehicle, the 260-D.

During the "fuel crisis," up to 80 per cent of the cars Mercedes sold in North America were diesels, more than 400,000 of them. With prices on the rise again, the possibility of cutting fuel costs by as much as 30 per cent should make diesels attractive again.

J.D. Power forecasts diesels will make up 15 per cent of the market in North America and Japan by 2015 compared to the current figures of 3.2 per cent and 0.2 per cent. Including the astonishing growth expected in China, diesel share of the market is expected to grow to about 30 per cent worldwide by 2015.

One of the developments expected to help diesel growth comes from Mercedes and is called BlueTec.

Diesel is a lower distillate, making it cheaper to produce. But that also means it is inherently dirtier. Mercedes uses a four-step process to reduce emissions:

Optimize engines and their combustion process to minimize in-cylinder emissions through cleaner fuel and such technology as electronic engine management, four valves per cylinder, third-generation common-rail injection, variable nozzle turbochargers and exhaust gas recirculation;

Use oxidizing catalytic converters to minimize emissions of carbon monoxide (CO) and unburned hydrocarbons (HC);

Use particulate filters (introduced by Mercedes in 2003) to remove 98 per cent of the soot particles, and;

Reduce nitrogen oxides, which remain the only component of diesel exhaust with levels above a gasoline engine.

This last step is the basis for BlueTec, which will be used on the E320 CDi coming this fall when the new cleaner fuel will be available.

The BlueTec process starts with several advanced catalytic converters and a particulate filter. One of the catalysts stores nitrogen oxides and is regenerated at regular intervals, producing ammonia and reducing the NO{-x}.

Another converter downstream uses that ammonia to cut nitrogen oxides even further, leaving nothing else behind other than harmless nitrogen and water found in the air we breathe.

A second BlueTec process involves injecting a tiny amount of fluid into the exhaust stream, and it is even more effective. To be used on the same engine in the new GL-Class SUV this fall, this process is already in use in Europe on more than 10,000 commercial trucks.

After the exhaust gases have been cleansed, a precisely measured amount of urea is introduced into the exhaust. This results in the generation of ammonia, which divides nitrogen oxides into nitrogen and water vapour. BlueTec thus cuts nitrogen oxides by about 80 per cent.

Mercedes refers to the harmless aqueous solution as "AdBlue" and it is carried in a small tank in the spot normally used for the spare tire. Each tank is sufficient for the mileage between regular service intervals, at which point the technician will refill the container.

This second BlueTec system allows a diesel to meet the toughest emission standards in the world, including those proposed for 2009. This should be of particular interest on this side of the Atlantic where bigger and heavier vehicles are popular because diesels are known for their tremendous torque, which better suits not only that vehicle type, but our driving habits.

For example Mercedes says the GL320 diesel will average or 9 litres per 100 km.

Look for this technology to make its way to other DaimlerChrysler products as well, such as various Jeeps.

globeauto@globeandmail.com

The rules

Regulations regarding the amount of sulphur permitted in diesel fuel were introduced in 2004. The goal was to ensure sulphur levels did not impede the use and effectiveness of emission-control technologies available on new vehicles and engines.

The requirements were aligned with those set by the Environmental Protection Agency (EPA) in the United States. They call for a decrease in the current levels of 500 mg per kilogram of fuel to be cut to 15 mg/kg in June for production and imports and Sept. 1 for sales, allowing time for the old fuel to be sold off and the new fuel to be available coast to coast.

But, because fuel moves through pipelines, tankers, storage tanks, bulk plants and service stations that have previously contained fuel with the higher levels of sulphur, there existed the chance of contamination of the new fuel by the old. So the regulations were changed to 22 mg/kg for a 45-day "grace" period from Sept. 1 to Oct 15, 2006.