Can we estimate Zn/P from sulphated ash content?

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I read in the forum that sulphated ash amount for total detergents, dispersents and ZDDP, etc. Now if we know the TBN value since it's mostly reported by oil manufacturers, can we make a guess on ZDDP? Just curious about the answer.
 
When the oil is ignited in the presence of sulfuric acid the test measures the residual ash, which represents the metallic components of the oil. The results are reported as a percentage and the test is not specific to zinc. Infer what you will from that.

What application do you have where you’re worried that a particular oil does not contain sufficient ZDDP?
 
When the oil is ignited in the presence of sulfuric acid the test measures the residual ash, which represents the metallic components of the oil. The results are reported as a percentage and the test is not specific to zinc. Infer what you will from that.

What application do you have where you’re worried that a particular oil does not contain sufficient ZDDP?
Just learning about it. Maybe someone knows how to estimate ZDDP from knowing sulphated ash amount and total base number.
 
Just learning about it. Maybe someone knows how to estimate ZDDP from knowing sulphated ash amount and total base number.
The problem here is that the DI package may contain other chemistry that has sulfur atoms contained within their associated molecules, such as MoDTC and calcium sulfonate detergents, and other components that may use sulfur in their molecular structure.

So I don't think you can take sulfated ash as an indication of ZDDP content alone.
 
Plus I’m pretty sure that the sulfation reaction is not discriminatory towards zinc. So I think any metallic element present for the most part will register as a result for the test. Phosphorus would create a volatile compound that would not influence the result.
 
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