Originally Posted By: 2010_FX4
I used Motorcraft air filters for the first 65K or so of my FX4's life and then switched to NAPA Gold. The NAPA filters seems to fit the airbox much better than the MC ones did and the quality of the filter is top notch. I saw a reduction in silicon levels (from 19/20 to 11/12); more monitoring to follow of course, but I would say that NAPA filters are excellent for the price.
The NAPA Gold air filters are made by Wix. Motorcraft air filters are made by the Dana Corporation (parent company of Wix) and are essentially the same filter. However, I have also seen where Motorcraft has supplied out some applications to Fram but built to the same Ford specifications. It is interesting that Ford pulled all the Fram built Motorcraft air filters for the 2004 - 2007 F150s and replaced them with Dana, but there are still Fram built filters in the inventory. Dana built filters have dark brown media while Fram are a light yellow. Both seem like good quality filters manufactured in Mexico. I was impressed with the Fram quality of the filter and packaging (sealed in plastic bag). Both manufacturers claim 98.5% efficiency per Motorcraft specification.