Sources of Calcium
Calcium is an additive metal commonly used in detergent additives. Only when the calcium level deviates more than 25% from the new oil or reference value should a concern be raised, but the likeliest cause if mixing or topping-off with a different product.
With normal and expected additive depletion due to usage, the additives are still present in the fluid, and will still be measured at their normal levels. Once they do not appear in the fluid, they have dropped out completely, which indicates a more severe degradation mechanism or additive drop-out.
Calcium may also appear from the use of granular oil absorbent products like kitty litter. These products are made from Fuller’s Earth, which is a magnesium- and calcium-based clay, that has an iron contaminant. Proportional increase in calcium, magnesium and iron, as well as particle count, often indicate ingression of this abrasive particulate.
Calcium and magnesium may also appear proportionally due to hard water contamination, which may lead to rust or corrosion, correlating with an increase in iron and possibly water content, if it has not been drive off by heat.
In mobile applications, calcium may also be found in road dust, and will increase proportionally with magnesium and particle count, and possibly silicon and/or aluminum.