Calcium vs Magnesium

[Scuderia]

Which one is the better detergent? I know there probably won't be a simple answer to this, but I've always wondered why some oils have like 3400 PPM of calcium and almost no magnesium, and others will have like 1200 PPM of calcium and 900 PPM of magnesium (total 2200 PPM)? How exactly do they each work, and why do the oils that have a lot of magnesium generally have less total detergents?

 

[INDYMAC]

I'm not sure how you can compare the two metals as detergents/dispersants until you know the solvency of the base or carrier oils being used by the blender. I would expect that blenders probably look at price first, but if there's a solvency issue then it might not work in their blend. I seem to remember Molakule discussing his preferences and he seemed to like Ca over Mg because it was a softer metal.

 

[Hoosier_Daddy]

meaning Ca can double as anti-wear, perhaps?

 

[addyguy]

Exactly.

I've read that Mg is actually a 'stronger' detergent, but it is far more abrasive than Ca., so blenders don't use it as much as they used to - it's a very 'old school' detergent compound.

 

[Hoosier_Daddy]

why then do HDEO's lean so heavily on Mg?

 

[Pablo]

Neither is a detergent.

Most of these type of questions have been covered nicely by Mola in the question of the day section.

https://bobistheoilguy.com/forums/threads/additives-detergent-dispersants.41162/

I forgot to add that some of the new technology CJ-4 HDEO's have much higher Mg levels, ie their detergents are also Mg+ based, not all Ca+ based. This is to keep a high TBN, but not have a high SAPS. The Mg "abrasive" thing is sort of blown out of proportion in typical BITOG fashion, IMHO.