Question: Thanks for the additional information in "More Black Oil" in the November/December 2011 issue of Truck Trend. What specific diesel oil should be used to adapt to this higher demand?

Answer: In an answer to another reader's question, we touched on the oil categorizing systems. There, we focused on gasoline engines, and the current oil ratings approved by most automotive manufacturers. As engine technology and fuel content changes, it's that much tougher on motor oil performance and longevity. Therefore, motor oil formulation must keep up with the harsher environments.

For gasoline engines, American Petroleum Institute's (API) and International Lubricants Standardization and Approval Committee (ILSAC) provided us with SM and GF-4 (respectively) oil formula standards since 2005. Then in October 2010, they converted to SN and GF-5. General Motors is the exception, providing its own oil standard known as "dexos 1."

It's a similar situation with diesel oil standards. This time you want to focus on the API rating of CJ-4, which was introduced in 2006 (replacing C-4). This oil formula standard was designed to deal with the latest diesel engine technology, including the use of an exhaust gas recirculation (EGR) system. And, of course, GM's got its own standard of "dexos 2" designated for use in the Isuzu-built Duramax engines. As in most cases, you should never use oil of a past rating in a newer engine, but it's OK to run a new oil formula in older engines (gas or diesel). Consult your owner's manual and/or local dealership service department for correct oil grade, classification, and service interval. Typically, motor oil of a big name brand bought over the counter is going to be the latest approved formula. But it can't hurt to check, and the information will be clearly printed on the label.


How To Reach Alex
If you have a technical question regarding your pickup, SUV, or van, feel free to contact Alex, a master technician with the National Institute for Automotive Service Excellence. Send a letter to him in care of Truck Trend Garage, 831 S. Douglas Street, El Segundo, CA 90245, or e-mail us at trucktrend@sourceinterlink.com. Please include the VIN with your question. Due to the volume of questions received every month, we cannot guarantee that everyone's question will be personally answered or will appear in the magazine.

Can't wait for help with a problem you're having with your Truck or SUV? Ask the expert we trust here at Truck Trend Garage -- visit Alex Steele at www.RealWorldAutomotive.com.