Purolator, but to Ford specs
Penz oil
Any place that sells Motorcraft oil filters will have an application chart showing you which one fits your Focus.
WIX makes all of NAPA's oil filters
Champion Filters (not connected with Champion Spark Plugs)
Ashland makes the oil to Kubota spec
I work at a carquest auto parts store and believe that kendall makes motorcraft oil. The bottles are exactly the same, only different colors. Ive also seen on the internet that kendall makes it.
Champion
hastings
Purolator
You do not have to use OEM filters. You should however use a quality filter. Purolator, Wix, Bosch, AC/Delco, Motorcraft, Mopar, and all OEM filters are quality filters. Avoid cheap no name filters.
Motorcraft, Purolator, Wix, or Bosch all make quality filters.
Purolator, Wix, Bosch, AC/Delco, Motorcraft, NAPA, & Carquest, are all excellent filters.