Oil Catch cans:
Frequently asked questions (and a few that you may be wondering about.......)
Does my vehicle need a catch can?
Answer: From a long-term prospective, every vehicle can
benefit from using a catch can, since no crankcase ventilation system from the
factory removes all oil from the blowby gasses that are recirculated back into
the engine.
How much oil will my catch can collect and how often will I
need to empty it?
Answer: That really depends
upon how much oil is being pulled from your engine's crankcase. Determining
factors include:
a) Size of
your engine (larger engines typically generate more blowby oil)
b) How well
your engine's piston rings are sealing against the cylinder bores (Older engines tend to produce more blowby oil but many newer engines, especially of V8 size,
can produce quite a bit of oil)
c) Your driving habits: Frequent low-load, high RPM driving often
promotes higher levels of blowby oil. (Blowby gasses are gasses that escape past
the piston rings and end up in the engine's crankcase.)
We recommend that you check the catch can's oil housing within the first 200
miles. Increase this length of time if more than a half-oz (approximate amount)
of oil (level must be below the bottom of the filter element) is not seen in the
housing.
How often will I need to change my filter element?
Answer: The filter
element is a very important part of this catch can system and should be changed
whenever vacuum pressure between the filter and the PCV valve decreases by 1.5
inches of mercury or if you have driven 5000 miles after installing or replacing
the filter - whichever occurs first. Keep in mind that oil containing a high
level of contamination will clog any filter media at an accelerated rate.
What can you tell me about those
inexpensive EBay catch cans?
Answer: Most of those "cans" contain no filter
element whatsoever. This means that only bulk (vs airborne) liquids will be
trapped. Unfortunately, the majority of blowby gas oil droplets are extremely
small in size - so small that these micron-sized droplets remain airborne all
the way into your engine.
Won't a $20 Home Depot or Lowes general purpose filter do the
same thing as your catch can?
Answer: We have tested quite a
few types of filer media and have found the flow characteristics and filtering
ability of the filter we use to be very effective at trapping oil, water, and
particulates, given the low pressures and flow rates associated with V8 engine
PCV systems. While an inexpensive store-bought filter will trap at least some
oil, keep in mind that:
a) The clear PVC housing of such filters has a temperature limit
rating of 125 degrees F. Most engine bays become much warmer than that.
b) Some fuels and oils may attack the PVC housing, which is
intended to hold primarily water.
c) The micron rating and flow capacity of the filter may not be
provided by the manufacturer or store of purchase. It is unlikely that the store
sales personnel will know this information.
What other types of filters have you tested?
Answer: We have tested wire
mesh, filament-wound, non-metallic, and other types and were somewhat alarmed at
the number of loose strands/fibers that tend to separate from the filter bundle.
The filters that we use are constructed of a continuous, porous layer of
material that can withstand 180 degrees without any degradation. Although
stainless steel wire mesh filters can withstand higher temperatures, their
propensity to allow loose strands to detach has prompted us to warn against
their use in PCV systems.
Wouldn't I be better off with one of
those large, wide catch cans?
Answer: The wider the
"can", the more likely collected oil will slosh around and re-enter the
airstream. This is especially true of systems that direct air flow through a
filter and then into the reservoir (can) of oil and water. The last thing the
airstream should "see" is the filter, not a sloshing body of fluid.
