IMO ... Ford panic'd and broadcast out a notice when CK-4 came out; based upon a drop in phos in that designation. They claimed that "testing" indicated accelerated valve train wear in the 6.7L, but would not ever produce any proof to any credible source when requested; we were just supposed to take their word for it, even though the entire rest of the HDEO market (OEMs and lube makers) all seemed to find CK-4 perfectly acceptable. Then on top of that, they simply said that ALL engines in their previous diesel fleet would be spec'd for CJ-4; right - as if they spent thousands of test hours and hundreds of engineering hours on engines they don't even make or warrant any longer (6.0L, 7.3L, 6.9L). That's a load of manure. I worked at Ford for 16 years, and I work for another major OEM in HVAC now; there is no OEM that spends oodles of money testing products on stuff they no longer make, just to throw out a maintenance recommendation. Ford did this at first as a knee-jerk reaction to their perception of an input in the formulation, without understanding the true nature of the outputs. Either that, or they make their valve-train components out of some uber-sensitive material that the rest of the world does not have access to, and now they are in a unique position to be the "only" one needing a super-duper spec, which interestingly enough, MANY CK-4 products are approved for ....
It's not like this is the first time Ford's fluid spec got them into issues, either. I believe much of the infamous 6.0L coolant issues were mainly due to Ford's use of their G-05 extended life coolant, which ultimately precipitates solids, being caught in the tight passages of the oil/water heat exchanger, which causes all manner of ills up and down stream in the cooling system. Navistar (designer/builder of the 6.0L) never spec'd that coolant; they first stuck with traditional green EG coolant with anti-cav additives, then moved to the their own Fleetrite red ELC as I recall, and their issues were FAR, FAR fewer in this topic. Hmmmmmmm .... maybe Ford should not try to out-think the rest of the market in terms of fluids.
Also, somewhat on topic (at least to the 6.0 and lube) is that Navistar spec'd the VT365 for 10k mile oil changes (or other limits)
See here; page 41 (search "VT365 engine introduction" and open the PDF)
[PDF]International VT 365 2004 Engine - 7.0 Navistar x234a custnav
www.navistarlearning.com/dotnet/application/downloadcontent2.aspx?...
"
ENGINE FACT:
The service interval for the engine oil and filter is 10,000 miles, 350 hours, 1,000 gallons of fuel, or 6 months."
Note that the equiv limits would be around 28mph avg, or 10mpg avg. The "or 6 months" thing is bogus IMO; oil has been proven in countless UOAs to not care how long it sits in the crankcase.
Those who change the oil frequently in the 6.0L can do so with the confidence they are wasting oil just like most every other BITOGer.
