I have noticed a trend in the concentrations of calcium and magnesium in diesel crankcase oils. When one increases the other usually decreases proportionaly. I am interested to know more about this phenomenon and the chemistry involved.

Is it?

Lube oil blending is a fascinating science and I love learning how it's done. Calcium is known more for detergency and magnesium is better known as a dispersant. Calcium levels, when too high, limit the treat rate of anti-wear additives. This might explain the cult-like following of one of the major oil co.'s 15w40's. Every user agrees that they like it's performance because when an engine is down for a major it's found to be spotless inside. Too bad because of the low anti-wear levels the re-build is being done way too early. Needs bearings but it sure is shiny . Much better value in an enhanced oil with the proper amount of anti-wear additives and magnesium to act as a dispersant .