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Address Reported Spikes in Iron in Used Oil Analysis
 
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Question:
Address Reported Spikes in Iron in Used Oil Analysis
Many UOA (used oil analysis) show spikes in Fe (Iron). Why is that? Rumors include chemical reactions to the oil additives and some other claims say that Mobil 1 causes higher than normal wear when in contact with iron parts. I am concerned about using Mobil 1 after seeing the results.  An official answer would be greatly appreciated.
-- Steven Hsing, Fremont, CA
Answer:
Iron particles in used oil are to be expected as the iron in engine components – such as cam shafts, timing chains and gears, piston pins and rings and the cylinder liner – wear down during normal operation. To determine if the level of iron particles is higher than it should be, a wide range of factors need to be assessed. These include whether the car is driven in normal or harsh operating conditions, the amount of highway driving versus city driving, whether the engine is subjected to stop-and-go driving, and the volume of cold starts and temperature extremes the engine endures. Also, the car and engine model, and the frequency of oil changes will have a significant effect on how much iron ends up in the motor oil.
 
All these factors can impact the amount of iron that goes into the motor oil, so it is necessary to consider all of these elements when establishing what a typical level of iron should be.
 
Also, used oil analysis is only one dimension when it comes to assessing engine oil performance. Ultimately, used oil analysis should be combined with engine inspections and measurements to more accurately assess the performance of the oil.
 
If iron content of a used oil analysis is considered higher than expected, the next step is to determine the cause of the premature wear. In order to do this, evaluate other data points from the used oil analysis report to obtain a more complete picture as to what's going on in the engine. Premature engine wear is often due to mechanical issues, not the oil. For example, elevated levels of lead and/or copper, particularly in combination with a positive glycol dilution test, would indicate that there may be a coolant leak within the engine. Coolant dilution in the engine oil (which would occur from something like a crack in the head gasket) would cause rapid acceleration of wear metals in the engine oil.
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