Guidelines with Oxidation and Nitration Numbers Needed

[LargeCarMan]

I thought this might be a helpful post and figure this will fit in the general lubrication topics post.

Can someone explain the Oxidation process in oil degradation process and the numbers scale on an oil analysis?

and

Can someone explain the Nitration process in oil degradation process and the numbers scale also.

These are very important and I need to get a handle on the how, why, and when to deal with them and the analysis does not give guidelines.

 

[LargeCarMan]

Thought I would bring this post back to the top of the list.

On the back of the analysis paper, it say's that Oxidation causes increased viscosity and acid formation and Nitration causes sludge and varnish formation. It also states that Solids reflect both oxidation and nitration issues from overextended drain intervals.

A guidline on numbers would be helpful for us to keep our oil in that range and not allow sludge,acid, and solids formation.

 

[TooSlick]

The method Oil Analyzers use shows the data in terms of "abs/cm" using an FTIR machine, which isn't going to mean a lot to a typical user. Limits for conventional oils are generally 30 abs/cm and for full synthetics they're 50 abs/cm. However depending on the application, the TBN or viscosity or silicon levels may be the limiting factor in how long you can run the oil and not Ox/Nit.

In the case of your recent analysis of the Amsoil ACD product, the TBN is @ 3.35 and I'd use a lower limit of 2.0. So this oil only has maybe 1000-2000 miles of useful life left.

Another method is to track the viscosity increase, which is directly affected by levels of oxidation/nitration. When the viscosity has increased by 20%-25% from the baseline value, I'd change the oil, even if there is still some TBN reserve left and the wear rates look normal. That level of viscosity increase means you are suspending lots of solids in the oil and it's time for a change.

TS

 

[LargeCarMan]

Quote: "Another method is to track the viscosity increase, which is directly affected by levels of oxidation/nitration. When the viscosity has increased by 20%-25% from the baseline value, I'd change the oil, even if there is still some TBN reserve left and the wear rates look normal. That level of viscosity increase means you are suspending lots of solids in the oil and it's time for a change."

Thanks...This method makes since and is a fantastic way for the layman (folks like me) that can look at the weight viscosity baseline add the 25% and know what you want to stay away from...

Excellent advice and thank you TooSlick.

 

[Pablo]

The only real way to speak % NIT and % OX in a UOA, is by comparing it to the virgin oil, I mean the same oil (same batch that went in, not just some other VOA) in the virgin state.

So you get a baseline on the FTIR, then you can compare it to the used oil. So the VOA baseline is 10 (or whatever) on the 0-200 scale, and the UOA is 30 (or whatever), then you can calculate a percentage.

To address the other points, I'll just add that oxidation can also cause sludge as well.

 

[Gary Allan]

This still seems to be a mystery science here. I guess we could term it an "additional complication" in terms of OCI length.

That is, an OX/NIT "table" would not be a single criteria for changing oil ..or rather would be trumped by other indicators (typically) before it became an issue

 

[TomJones76]

Caterpillar seems to agree with Tooslick on this.
Note their condemnation limits re: viscosity:

http://www.natrib.com/publications/appnotes/app24.php

Of course, that's for diesel, but similar principles apply. In diesel engines, soot tends to THICKEN the oil. In gas engines, if your fuel gets in, it tends to THIN the oil...

Here's some guidelines for gas engine alarm limits:
http://www.natrib.com/publications/appnotes/app30.php

 

[LargeCarMan]

Very good info TomJones76....