Volkwagen has been selling diesel-powered cars in the U.S. for almost 30 years. Turbocharged versions have been available for 25. That is a lot of experience and a testament to the development of a reliable, efficient and durable powerplant. The introduction and development of the TDI (turbocharged direct injection) brought the VW diesel into the new century with a big head start on any competition. With the exception of Mercedes-Benz, VW has been the only manufacturer to sell diesel passenger cars in this country in any great numbers.

Diesel power may not be for everyone, but I would guess that many people would not even realize that a TDI was diesel powered unless they were told. Compared to the diesel-powered cars of 20 years ago, the TDI is quiet, powerful and smooth. Economy of operation runs the gamut from the high fuel mileage, to the lack of needed tuneups.

Since there are no longer any adjustments to be made for valve clearance, timing or cold weather operation, maintenance is limited to oil changes and filter replacement. Even extended-mileage timing belts are now available that can extend the period between replacement. Depending on climate conditions and type of use, I would be comfortable extending the service interval for timing belt replacement to 80,000 miles as long as one of the extended-life belts is used.

With all that good, there is a maintenance problem that has taken a toll on the low cost of...