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Lube Filtration

Overview

Full Flow, By-pass or Typical Engine Lube Filtration System LUBE FILTRATION
Two-Stage Filtration

The difference between the various Full-flow Filter By-pass Filter (or
lube filter configurations can be secondary)
confusing. There are conflicting
views in the industry as to which
option is best. There are three
common filtration approaches. A brief
explanation of each is below.

Full Flow Filtration
Full flow filters receive near 100% of
the regulated flow in an engine lube
system. Full flow filters provide essential
engine protection for maximum cold flow Pump
performance and filter life. Most lube filters Sump
available today are full flow. Oil Galley

By-pass (secondary) Filtration
By-pass filtration is when a small portion
of the system’s oil flow – usually 5-10% – is
diverted back to the sump or oil pan before
reaching the primary filter. A bypass filter
captures smaller particles than the full Typical Lube Circuit
flow. Because of the increased efficiency of
a bypass filter, they are more restrictive. To
optimize restriction, a bypass filter should Engine components to
be located in a separate flow path, as be lubricated
illustrated on the right.

Two-stage Filtration Full Flow Filter
A two-stage filter design attempts to
combine the features of both a full flow
and by-pass filter. The two-in-one design
significantly increases restriction, causing
shorter filter life and decreased cold flow By-pass Filter
performance. Poor cold flow performance
starves the engine of oil during start
up, leaving the engine temporarily
unprotected. This will lead to increased
engine wear that may result in premature
repairs or even engine replacement.
Pump High Pressure
Relief Valve
(135 psi / 931 kPa)

Return Flows to Sump

Sump or Oil Pan

www.donaldson.com Engine Liquid Filtration • 67