Table of Contents

Prefilling Oil Filter Instructions

The Cummins manual states:

Fill the oil filter with clean lubricating oil. The lack of lubrication during the delay until the filter is pumped full of oil is harmful to the engine

IF you do pre-fill the oil filter, there is a right and wrong way to do it.

The small outer holes are the INLETS, the large center hole the OUTLET.

Pour all the oil in the small holes. Any oil that gets in the (much easier to hit) large center hole will go to your engine UNFILTERED. Do not assume there are no particulates in new oil (ask any Petroleum Products Engineer).

Many go to a hardware store and find a short pipe that threads into the center hole while pre-filling to keep oil from the OUTLET hole.

BTW, Caterpillar recommends AGAINST pre-filling filters for just this reason – fear of particulates in oil passing directly into bearing areas.

Is new oil really Dirty?

The following values are for oil taken from a newly opened container and submitted to an analysis lab.

Prior to 1999, ISO Codes were expressed as two numbers, such as “14/11” (as seen in the below chart), these represent the ISO code for found particles greater than 5 microns and greater than 15 microns (see code chart below). This chart also includes larger particle counts, those for >75 microns >50 microns >25 microns as actual counts (not as an ISO code)

Oil ISO Clean Particles per Milliliter
>75um >50um >25um Notes
Cenex 15W40 23/17 2 9 115 (1)
Synlube TMS 10W30 20/15 0 0 9
Chevron 10W 18/13 0 1 16
Chevron 15W40 19/15 2 9 35
“Unispec” 20/17 0 4 177
Farmland 15W40 20/15 12 24 72 (2)
John Deere 10W30 19/13 0 2 9
Mobil 10W30 19/15 1 3 41 (3)
Mobil Delvac 15W40 22/16 1 4 50
Rotella 15W40 19/14 4 8 28 (4)
Royal Purple 5W30 18/14 0 8 28
Schaeffer 15W40 18/13 2 3 12
Mobil Delvac 1 20/14 0 1 19
Cat Deo 5W40 18/12 0 1 5 (5)
M1 0W40 21/16 1 2 54 (6)
M1 Truck SUV 21/15 1 1 16
Synergen 15W50 18/13 5 14 25
Mystic 5W30 17/13 1 2 7
Amsoil 15W40 19/16 1 6 64
Pennzoil 15W40 17/14 1 13 93 (7)

(1) Contained metal flakes “not uncommon in new oil”
(2) Contained 8 particles/ml over 100um (0.004“). Caterpillar have an ISO 16/13 spec for new fill (and that most bottled oils don't make it).
(3) Dust/debris seen in microscope, recommend filter before use.
(4) 2 particles per ml greater than 100um (0.004”)
(5) One would assume that being Cat, it was pretty well filtered to suit their case.
(6) Noted small particles that appeared to be organic, possibly additives
(7) Noted that this oil has an additive that shows false Antifreeze.


ISO 4406:1999 Code Chart

ISO 4406:1999 Code Chart
Range Code Particles per Milliliter
More than Up to/Including
23 40000 80000
22 20000 40000
21 10000 20000
20 5000 10000
19 2500 5000
18 1300 2500
17 640 1300
16 320 640
15 160 320
14 80 160
13 40 80
12 20 40
11 10 20
10 5 10