The new CK-4 diesel oil specification prompted Ford Motor Co. to issue a technical service bulletin warning Ford owners not to use it in their 6.7-liter diesel engines.
The CK-4 diesel specification removed the valvetrain wear test (ASTM-IIIG) used on all previous diesel specifications, like the CJ-4 diesel oil spec. Ford 6.7-liter owners should continue to use CJ-4 spec diesel oil.
Many hot rodders, racers and classic car owners have used diesel oil because it had a higher level of ZDDP, according to Driven Racing Oil’s Lake Speed Jr., as you’ll see and hear in the video below.
Driven’s Speed Jr. brings clarity to the proceedings, and provides resources for further education. Check it out.