Dear Truck Trend,

Regarding the Ram Heavy Duty: I would make the case that unless an owner intends to pull heavy on the Interstate more than 90 percent of the time, he shouldn't buy the Cummins, because of its emissions problems. Please do a Web search for Dodge 6.7 problems and read on. There are complications and user-annoyance issues with the EGR and DPF on the 2007.5 and 2008 Dodge Cummins trucks. As the unhappy owner of a 2008 6.7 Cummins, let me list some of its limitations and the things you are likely to learn after you visit the dealer for the check engine lights:

(1) Not supposed to idle longer than five minutes as it produces excessive soot. Want to warm up your truck on a cold day or go through a drive-thru?

(2) Supposed to run the exhaust brake all the time to help keep the turbo from clogging up with soot. There are situations like snowy conditions where you don't want to use an exhaust brake.

(3) Please discuss the DPF's regeneration process. The overhead will alert when the DPF is 80 percent full, at which time the driver is to "simply" drive over 45 mph for 45 minutes without stopping for the system to clean itself. The truck tells the operator when this needs to be done, not vice versa.If you don't do so immediately, 80 percent can go to 100 percent full within a few blocks, not miles. If the system decides the catalyst is full, the truck derates itself into what's known as limp mode and the driver can limp at 25 mph to the nearest dealer. The truck doesn't care if you're late for an appointment, are just arriving at your destination, or experiencing rush hour. This is known as active regeneration where fuel is injected on the exhaust stroke thereby increasing temperature to clean the exhaust. Passive regeneration is whereby the truck is under heavy load and producing high exhaust temps on its own. Doesn't work too well in cold climates either way in my opinion. If catalysts on gasoline engines required the driver to "simply" drive for 45 miles at greater than 45 mph, they wouldn't be around, but emissions on gasoline engines are trouble-free.

(4) The EGR system pumps exhaust back into the intake, where the soot makes the engine oil black almost immediately after a change, perhaps contributing to the limited turbo life on these trucks.

(5) Abysmal mileage versus the 5.9-liter, which didn't have all these emissions devices. Perhaps on a brand-new emissions system you can get 18 mpg, but give it a few miles and expect more like sub-15 mpg unloaded.

(6) Emission system costs and just general ownership costs. There are six sensors in the exhaust alone. To replace the various emissions devices in the exhaust system is $7500 for just the parts.

(7) I had my turbo replaced at 21,000 miles. Many owners have had this happen. Check-engine lights are a constant problem. Dodge has come up with numerous "flashes" for the ECM to try and curb (but not solve) the issues. Bottom line is the 6.7 won't work trouble-free except for owners who haul heavy and often due to the emissions systems. Perhaps I could trade for that Power Wagon. I am sure I'd take a huge dollar hit on my Cummins, however in the long run, I might be much better off.

Doug Bithell
Omaha, Nebraska

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Dear Reader,

We went right to the source, asking Ram Truck to address your concerns: "The Cummins turbodiesel engine has an advanced diesel exhaust emissions aftertreatment system which we pulled forward several years ahead of federal requirements. (This new type of diesel particulate filter has been used in Europe for several years.) Typically, the filter "desoots" itself in the course of the customer's normal driving pattern. We found the duty cycles of a small number of customers did not adequately clear the filter, and as a result we've made significant improvements in the system since the initial launch. We have developed software improvements--available to all customers, including owners of 2007-2008 models--which will resolve the issue. These improvements place no restriction on idle time or use of the exhaust brake. These changes have been incorporated in the 2010 model-year Rams, allowing them to meet the high quality levels of our previous generation diesels.

Relative to the desoot process, the sequence of events described can't happen if the system is operating properly. After receiving the 80 percent notification, the customer will have approximately 30 minutes on the worst-case operating cycle before reaching the 90 percent message, and another 90-plus minutes beyond that to reach the system full message. On normal cycles, the system will execute the regeneration process. To reach the messages faster than these times, there must be a malfunction in the system, such as an air leak, etc. The customer should return to the dealer for a full diagnosis and repair.

Regarding fuel economy, it is true that all aftertreatment systems required by the emissions regulations impose some penalty on fuel economy versus older engines. However, fuel economy will improve with mileage as the engine and driveline system break in. The darkening of the oil is not an indication of the service life. The engine system calculates the vehicle usage impact on oil quality and displays a message when an oil change is required." Please let us know if that helps answer your questions.

--Truck Trend

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