Its part of that companies part Number System and means "Oil Filter" and I have no idea how the got from oil to pH.
PH-30 oil filter
Ph 8172
fram ph 10968
PH 3614
PH8170 is a lawn tractor oil filter...
Fram PH 3614 Fram PH 966B Fram PH 2870A Wix WL 7142
PH-8170
Fram PH 4967
ph-16
ph-43fp or ph-43
Fram PH/2
Napa oil filter 1311 equivalent to Fram pH 7328