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Read our primer articles on Oil Analysis and Tribology

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You don't mention what type of engine and lubricant type.
On the assumption we are talking about high speed diesels(vehicle engines)then Phosphorus is part of the additive system almost always in conjuction with zinc(ZDDP)and at levels approximately 1000ppm for both in the oil.
If the level and/or proportions of Zinc and phosphorus have changed then different oil may have been added(gear or ATF). Check also Calcium levels for changes ,TBN and viscosity.
Also labs are not infalible, resample and retest!
We have slow speed (100 RPM) diesel engines with crossheads. We use Exxon mobil's Mobilgard 570 cylinder lubricating oil. The cylinder oil sample was taken during a shut-down period and a high phosphorous content was discovered, approx. 101 ppm. My research is revealing a mixture of the cylinder oil with the system lube oil (Melina S 30 - Shell product). Is this what the high phosphorous represent?
Hi Harmu, Cylinder oil will be high in Calcium (70TBN)with a viscosity typically 21cst at 100C
System oil will contain Phosphorus and relatively low in Calcium (5TBN)and 11.6 cst at 100C.
Also Fuel will be a possible contaminant
You need fuel viscosity and ICP metals to check impurities like Vanadium Nickel in F.O.
Then by assessing all three you can get an idea of the contamination of Fuel and system oil.
Fuel will raise viscosity and show Vanadium etc
System oil will lower Vk and show Phosphorus and a lower Calcium level.
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