minisprint, you don't need the Ford brand SCA or their special 3-way strips. Any quality SCA and test strip will work wonders in your PSD's, including the NAPA brand.
FW-16 (or FW-15, etc.) is not a specification
. It is simply a Motorcraft part number like their FL-1995 oil filter. Ford only listed a SCA specification (ESN-M99B169-A) for a few select PSD's made in 2002, just prior to the introduction of their Gold coolant. You can verify that for each model year HERE
in the Owner's Diesel Supplement, and HERE
with Ford's Green/Gold Service chart.
NAPA carries the original, and most widely used type of SCA in the world. It's the stuff heavy-duty diesel truckers use. It's easy to find and easy to test. My fleet experience shows that this type of SCA is less prone to over-dosing, has a longer life, provides better cavitation protection, and is easier on your water pump and cooling system. It is Nitrite-based. Nitrite is most important and primary cavitation inhibitor. Unlike Ford's stuff that can't be balanced on the Molybdate/Nitrite scale, it does not rely on "synergy" to work. I guarantee you will like it. [img]/ubbthreads/images/graemlins/cool.gif[/img]
If you need industry accepted conversions and test methods between the two types of SCA, or information from the SCA makers saying it's ok to mix different SCA's, I can PM you that.
BTW, the guys at NAPA don't deal with Ford's SCA part number. If you mention "Coolant Additive", "Coolant Conditioner", "Supplemental Coolant Additive", or NAPACool, they'll know exactly what you want.