EP gear oil clearification

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Jul 17, 2006
SW Michigan, near Fennville
We are looking at getting an ISO 220 grade SGM gear oil for our Westfalia Seperator (centrifuge) and it lists certain spec in the manual. One of them is that the Corrosive effect on copper according to DIN 51759/100 A3, degree of corrosion 1. On some quotes we have gotten from Shell Omala VG220, Citgo SGM ISO220, and Amsoil SGM ISO220, they have different listings for the sopper strip corrosion. Amsoil is 1B, Citgo is 1B, and the Shell Omala Oil is 1a.

What is the difference between 1a and 1b? Is "1b" better than "1a" for instance?
All these products meet the copper strip corrosion test you mention.

The PAO based Amsoil product will last several times as long in service as a petroleum gear lube and save on energy consumption, so the prices aren't directly comparable.

ASTM D 130 is a copper cossosion test where copper metal strips are soaked in the test oil at 100C for 3 hours and then graded to a "scale" as to stain or color or residue.

1-4 class.
a-d sub class

1A is NO stain or corrosion at all
1B,C,D are slightly more corrosion or stain but the ALL of the 1 class ratings are considered NON corrosive.

Then goes to a 2 class and a 3 class and a 4 class which will show on the copper test strip as black/red residue.

For your gear box use a 1A or 1B will be OK.
Just wanted to give a shout out to Bruce for once again disseminating very useful information to the users here.
I too was wondering about the copper corrosion scores.
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