As noted in Jeff Bartlett's previous warranty blog, Chrysler is offering lifetime powertrain coverage on most of their models. Like almost everything in life (including taxes but excluding death), there are exceptions. In this case, they are SRT high-performance models and fleet vehicles. One particular exception seems glaring--diesels (and the Dodge Sprinter van) are excluded. Although gasoline engines can last a very long time, diesels still have a reputation for further longevity. So why doesn't Chrysler include them in this plan?

It's a guess, but a recent road trip to upstate New York gives me a hint. On that trip into farm country, I was surprised to see the number of well-patinaed Dodge Ram trucks on the highway. (Several of them were the pre-baby-Kenworth-styled version, making them at least 16 years old.) The common thread: they had the Cummins turbodiesel engine.

Buyers who made the initial investment in a diesel Ram or Sprinter, especially business owners, might be just those folks who would drive their trucks until the wheels fell off. They're the ones who would really benefit from lifetime powertrain coverage--even beyond the 7 years/100k coverage you get on a Ram diesel. John Ibbotson, our chief mechanic and expert in John's Tool Box (available to ConsumerReports.org subscribers only), tells me the replacement cost of those Cummins diesels, or the Mercedes diesels in the Sprinter and Jeep Grand Cherokee, are pretty high. Parts like injector pumps are expensive, too.

So, keep this in mind if you're considering a Jeep Grand Cherokee diesel or another Chrysler product with a diesel. Even though you might just use the vehicle to haul around your family, rather than racking up lots of miles running between various job sites or customer locations, you'll miss out on the extended warranty coverage trumpeted in Chrysler's ads.

--Tom Mutchler