Purolator, but to Ford specs
wix
According to fordparts.com : For a 1995 Mercury Villager : Engine oil filter ( Motorcraft FL - 839 ) Engine air filter ( Motorcraft FA - 1121 ) Engine fuel filter ( Motorcraft FG - 978 )
As far as I'm concerned, the Ford Motorcraft air filter. The mass air flow sensor wires on my 1995 are perfectly clean, and I have used nothing but Motorcraft air filters for over 12 years now. I know they are expensive, but sometimes you get what you pay for !
ford parts . com ( no spaces ) shows the ( Motorcraft FA-1043 ) engine air filter for the 1992 Ford Explorer
For almost 15 years I've used nothing but Motorcraft air filters on my 1995 Ford Explorer XLT and the mass air flow wires are still shiny clean I know there are cheaper air filters on the market but sometimes you get what you pay for ( as of December 13 , 2012 it has now been over 17 and 1/3 years )
According to the 2000 Ford Expedition Owner Guide : Motorcraft ( FA-1634 ) is the engine air filter used for the 4.6 and 5.4 liter engines
Any place that sells Motorcraft oil filters will have an application chart showing you which one fits your Focus.
Purolator makes their own filters along with many other brands. The company is owned by Clarcor. Clarcor make all types of filters for industry. Water, air, oil, automotive, & hydraulic filters. Their headquarters is located in Franklin, Tenn.
The Packaging. Autolite MAKES Motorcraft
Purolator filters are made by Purolator Corporation a Clarcor Air filtrations Products Inc. Purolator stands for "pure oil later". They make an excellent filter and make filters under many other names. They also are the manufacture of Bosch, Motorcraft, PowerFlo, ProLine, & Quaker State filters. I use Purolator exclusively on all my engines.
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.