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First of all i am very happy to find a forum about oil analysis. I am working as an engineer at a company which manufactures shock absorbers. During manufacturing prosess we deal with a lot of oil related problems. As you know shock absorbers are a kind of oil pump actually. We are forcing the oil to pass from very tiny holes and use reaction force for dumping. There are 3 main problems about that. First of all we need to know viscosity of the oil ( we only know it from supplier's statement, we must be sure). 2nd main problem is foaming. In most cases oil begins to foam while passing from little profiles with high speed. And it creates major failure for shock absorbers. As 3rd problem we need to know more about oil analysis and how to build our own lab.

I will be so happy if anyone bothers to answer my questions. Sorry about longness of the message...
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HI Murat,
Viscosity is the most important parameter for an oil, so the specification data sheet must be correct and representative. However, oils supplier can sale the oil with 5% + or - the specification. If the precision is very important, so you must do this test in a laboratory, why not in two laboratories (ASTM D445).
For the second problem (foam), i suggeste to read "Using Oil Analysis To Monitor the Depletion of Defoamant additives) in noria_learning_center, or other topics in this same center, a lot of trouble shooting are given.
oil Analysis: What you need is: spectrometric test (element analysis : wear element, additives and contaminants), viscosity, TAN/TBN (acidity or alkalinity of the oil) PC (particle count for filtrated oil), and water (by KF coulometric analysis).
Note that a can found a huge information on oil analysis in
I suggeste
Djaouida, thank you a lot for your answer, i will check learning center as soon as possible. We are planing to make investment for oil testing equipments but i don't know which tets and which equipments are suitable for us. I think tendency to foaming and viscosity test are certain and because of heat in shock absorber, flame point is also important, but i need suggestions for other tests...
Murta, many moons ago I was involved in supply of Shock absorber oils./fluids
Viscosity as you say is of prime importance but viscosity loss if VI improvers are used is significant.
Foaming too you rightly identify is a much more complex issue with solubility of gas in the base oil important.
Foaming is certain to take place also.
If I remember the only way to test shock absorber fluids is by rig testing in the shock absorber.
Yes my mail adress is, i will be so happy if you send some information to me... Thanks...

And as mentioned in subject Smile i really have a lot question to ask; while my tests on shock absorbers, i noticed that oil has a significiant effect on noise... But i can't explain/understand which specification of oil could effect working noise/vibrations... If anyone have any idea i would glad to hear it...
Hi Murat

Please notice that when oil passes through a small hole it will for a short period be subjected to high shear. If the oil contains VI-improver that will be a problem because the high shear will cause both a temporary and a permanent viscosity loss (break-down of the VI-improver). The best solution is to use an oil which has no VI-improver, but preferable with a high natural VI. A high natural VI is normally obtained by using PAO, ester and/or Group III base oils.
There is probably a relation between the oils viscosity and the level of vibrations/noise. Oils with higher viscosity (and/or no break-down of the VI-improver) will often reduce vibrations/noise.
The problem with foam is more complicated and I am not sure that you can solve it with focus on the fluid only, you will probably also have to take a closer look at the construction.
Hi Murat,
I have been developing oils for shock absorbers.The specifications of oils differ depending on shockab design and there are different shock ab oils for different shock ab manufacturers.The viscosity is the most important property as indicated by our other experts.this is measured by ASTM/IP method.Anti foam additives are added to take care of foaming and also antiwear additives.
There is one rig which simulates the operating conditions where one million strokes are given and the change in oil property is measured to chheck the suitability of oil Other physico chemical tests are also done for the oil.
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