Q: My 7.3-liter diesel, Big Red, is coming up for its first 14-quart engine oil change, and I have been looking through my Ford book for the correct diesel engine oil to put in the truck. What the Ford diesel book states is an alphabet soup for me. Ford indicates 15W-40 Preferred, Ford specification WSS-M2C171-C or API Service Categories CG/4/SH. It says, "Do not use oils labeled with only one of the following category designations; SG, SH, CE, CF-4, or CG-4, as they could damage the engine."

At AutoZone, I was advised to use Valvoline All-Fleet Plus engine oil SAE 15W-40, whose back label indicates it "meets or exceeds the following engine manufacturers' specifications: Cummins CES 20081, Mack EO-O Premium Plus 2007, CAT ECF-3, Detroit Diesel 93K218, International and Volvo VDS-4. In the circle, it indicates it exceeds API Service CJ-4, CI-4 Plus, CI-4, CH-4, CF/SM. AutoZone advised use of Shell Rotella T SAE 15W-40, Heavy-Duty Diesel Oil, which meets or exceeds about the same as the Valvoline oil, and "meets API service CJ-4, CI-4 PLUS, CH-4, CG-4, CF-4, CF/SM."

Because my 1997 Ford diesel manual was probably written around 1996, I can only assume that SG is now SM; SH is also now SM; I don't know what CE is now; CF-4 can now be CJ-4; and CG-4 can now be CH-4. That indicates that from 1997 to 2013, all specifications for diesel engine oils have been upgraded to the new specifications, and the Valvoline oil is safe to use in my 1997 7.3-liter diesel, but I do not know. I think in 1997, Ford diesel engines were manufactured by Navistar, and I do not see that manufacturer identified, but, as said, I do see Cummins, Mack, Detroit Diesel, International, and Volvo, and I think I see all the upgraded specifications. Can I use any of these oils, or should I continue to look for oils that adhere to the specifications in my Ford book?

A: Navistar is International. In 1986, International Harvester was renamed Navistar International and continued manufacturing trucks and engines under the International brand name. The 7.3-liter Power Stroke diesel is basically a Navistar T444E engine produced for Ford. So, with products meeting or exceeding International specs, they're referring to Big Red. The API (American Petroleum Institute) oil standards have been updated since the 1997 production year, and the diesel engine oils you've mentioned will work fine in your Power Stroke. Most of the time, when a manufacturer updates its product's motor oil requirements, the new blend will still apply to older engines. If you want to go straight to the horse's mouth, Motorcraft SAE 15W-40 Super Duty Diesel motor oil is what they'd pump in at a Ford dealership. It meets or exceeds API service category SM, "particularly recommended for use in Ford vehicles equipped with Power Stroke engines," and "can be used in older engines where the manufacturer recommends API Categories CD, CF-4, CG-4, CH-4, CI-4, and CI-4 plus."


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