“Clean diesel” fuel explained

September 22, 2009 -- Filed under Clean Diesel by Louis-Alain Richard

This blog has been online for a year now, and even though we’ve often dealt with TDI technology there still seems to be some confusion about the term “clean diesel.” For readers who are in a hurry, there are just two important points to remember.

- A Jetta TDI, or a Touareg TDI, runs on diesel of any type. All diesel fuels have low sulphur content and are therefore clean.

- So, at the pump, you won’t see “clean diesel” written anywhere.

Now, the long explanation:

The term “Clean diesel” applies to diesel fuels sold in North America, which all contain low levels of sulphur. Since 2006, this has been the only diesel fuel offered in Canada (since 2008 in the U.S.). Which is just as well, since the new generation of turbodiesel engines run exclusively on this type of fuel, whether on a passenger car, construction vehicle or transport truck. So it’s one fuel offered in two types, i.e. regular and super.

If you’re like me, you remember when we converted to unleaded fuel. The clean diesel conversion is similar. Back then, lead was removed to allow the use of the first catalytic converters, which would otherwise have blocked up with the heavy metal. Similarly, sulphur is not compatible with the pollution control systems on modern turbodiesel engines.

However, contrary to what happened with the conversion to unleaded (older engines couldn’t handle the new fuel), TDI engines of all generations can run very well on the new low sulphur fuel.

To avoid filling up with the wrong fuel, filler necks on cars requiring unleaded fuel used to be made smaller. With the conversion to clean diesel, there is no need to differentiate the filler necks, as high sulphur diesel is no longer offered on the market.

Some fuel pumps offer a bigger high-flow nozzle that doesn’t go into a regular car, but they’re reserved for trucks that can have tanks of up to 200 litres. The TDI can be filled up with one of these if a funnel adapter is used.

In conclusion, it should be note that “Clean Diesel” (with capitals) is a Volkswagen trademark. With the help of this brand, the German automaker aims to inform North American drivers about the differences between the old and new generation of TDI engine.

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