These filters are externally the same. Might be some internal difference. Both work on a small block Chevy. EDIT: According to the fram website these filters are the same basic size but the PH5 has an antidrainback valve and the PH13 does not.
Ph5
Ph5 Fram oil filter fits GMC 7.4L or the 454 cu. in.
Ph5 Fram oil filter fits GMC 7.4L or the 454 cu. in.
Ph5 Fram oil filter fits GMC 7.4L or the 454 cu. in.
It is a Fram Extra Guard Oil Filter.
PH5
Chevrolet small blocks
ph5
ph5
fram ph5
PH5