Clearing Up Ford’s Diesel Oil Statement

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In the July issue of NOLN, page 34, in the article titled “The New Diesel Engine Oil Standards and Ford’s Reaction to them,” you’ll find the statement: “At this time, according to Ford, SAE 10W-30 oils showing CK-4/SN cannot meet WSS-M2C171-F1 and should be avoided.” This statement may cause some confusion for some, so we reached out to a diesel oil expert to offer some clarification.

Dan Arcy is the Global OEM Technology manager for Shell Global Solutions and has years of experience working with diesel oils and diesel oil specifications. Here’s his insight into Ford’s statement. “The statement, ‘At this time, according to Ford, SAE 10W-30 oils showing CK-4/SN cannot meet WSS-M2C171-F1 and should be avoided’ is correct. However, as stated, it can be misinterpreted easily. This statement pertains to multi-vehicle oils that meet both the API CK-4 specification for diesel engines and the API SN specification for gasoline engines. The statement does not pertain to heavy-duty engine oils that meet CK-4 only and are not intended for use in gasoline engines.

“The details:

  • Ford recommends oils that meet and are approved against their WSS-M2C171-F1 specification.
  • Ford’s primary recommendation is 10W-30 viscosity grade. (Ford also allows other viscosity grades, as long as they meet WSS-M2C171-F1.)
  • Ford WSS-M2C171-F1 requires an oil to contain between 1,000 ppm and 1,200 ppm phosphorus.
  • This is where the distinction between the “C” category (CK-4) and the “S” category (SN) is important.
  • To meet API SN, an SAE 10W-30 grade oil’s phosphorus level must be below 800 ppm. (This is Ford’s concern.)
  • An oil meeting API CK-4 only in a 10W-30 viscosity can meet the 1,000-1,200 ppm phosphorus levels required by WSS-M2C171-F1; however, it obviously cannot ALSO meet the less-than-800 ppm phosphorus levels required by SN.
  • Remember too that not all CK-4 only SAE 10W-30 heavy-duty engine oils are approved against Ford WSS-M2C171-F1.
  • For instance, Rotella T4 Triple Protection 10W-30, which meets CK-4 only (not SN) and has approximately 1,150 ppm of phosphorus, meets and is approved against Ford WSS-M2C171-F1.

From a customer perspective, they should look for an oil that has Ford WSS-M2C171-F1 on the label and is the appropriate viscosity grade for the ambient temperatures they will be operating in.”

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