Description Fleetguard LF637 is a cartridge‑style lube oil filter for heavy‑duty diesel engines, providing nominal 30‑micron filtration efficiency (68%) to remove wear‑causing contaminants from engine oil; typical applications include Kenworth, Mack and White trucks and other equipment specified for this filter, and it cross‑references Donaldson LFP55‑0637 and P77‑9095, Fram C‑1720, NAPA 1637, Purolator PM‑6025, WIX 51637, GMC 25011956 and equivalent part numbers.