How do i know what the right oil filter to use is.?

so i do my own oil changes every 3kmiles i have a 2002 ford f150 V6 that takes 8Qrtz. ive always used castrol GTX oil with an STP Filter. i always buy the same exact oil filter because idk what size i should be looking for. the filter come in a bunch of different sizes and idk which i can use. if i wanted to get a different brand lets say FRAM or K%26amp;N how would i know what size to get.?How do i know what the right oil filter to use is.?in most stores they have a book there to look up your vehicle type, and it tells you the code # you need for all the filters.How do i know what the right oil filter to use is.?Most Auto shops have lists of specification for cars. Just visit an auto shop and ask for help about oil filters. Or you can try looking in your Owner's ManualHow do i know what the right oil filter to use is.?Stay away from Fram (Wal-Mart junk) all K%26amp;N products are a scam marketed to folks that don't know any better...For your vehicle I would recommend Wix p/n 51516, Purolator p/n SL20195, Ford Motorcraft FL-400S avoid all others. As far as afterrmarket oil filters Wix and Purolator are pretty much unbeatable from a quality / particle filtration standpoint.How do i know what the right oil filter to use is.?most stores have a cross reference chart on the shelf to look at but your best bet is to go to a parts store and tell them what type of a filter you want and they will give you the proper one.How do i know what the right oil filter to use is.?www.penzoil.com will tell you all you need to know ;)