Join Date: Dec 2009
Location: Mount Hope, Ontario
About a year ago I went through the exact same thing you encountered with your oil filter change.
The place I bought my used 06 6.0 ltr from early last year did a service on the truck before I picked it up, which included an oil change.
When it was time to do my first oil change, on advice from a friend of mine that is a mechanic with the Toronto City Works, I bought a Ford oil filter cartridge (@ $41.00 !!!). He said they had a lot of problems within their fleet trucks with using aftermarket filters.
Like you, when I removed the oil filter, I discovered there was a Wix filter and cap assembly in my truck. I removed the Wix cap from the filter and was going to use it with the Ford filter, but then noticed that the Wix filter is taller than the Ford filter!
You are correct, you can only use the Wix filter/cap as an assembly, if you use the Wix cap with a Ford, or any other factory fit filter, the oil will not get filtered, as it can bypass the shorter filter!
As mentioned above, you should change out your cap asap to a factory cap/filter. My mechanic friend said that they had so many problems (lazy start up, motor failures) with aftermarket oil filters, especially Wix, that they only use Ford, or International filters on their Ford 6.0 ltr truck motors.
I had to buy a new oil filter cap from Ford as well, get ready for it...................................for only $98.00! If I were to do it again, I'd buy one of those nice billet aluminum ones as they cost about the same, or less.
I now use International fuel and oil filters, they cost approx. half of what Ford charges for the same filters!