Larry Crider
CALL (866) 580-1008


If your oil meets the vehicles service requirements (API, ILSAC, etc.  rating) as per your owners manual and is within the time or miles allowed for the driving conditions that the vehicle is being used for; either by the vehicles manufacturer or the maker of the motor oil (some oils are designed for longer than factory drain intervals) then the color has little or no bearing on its serviceability.
Motor oils turn dark as they do their job of lubricating and cleaning an engine. You cannot look at used oil with the naked eye and tell its serviceability. This can only be found out by laboratory analysis.
Oil samples can be tested in the laboratory by spectrographic analysis. The Lab will test it for changes in viscosity, fuel dilution, wear metal content (microscopic particles of metals worn from the engines components in the oil and too small to be removed by the oil filter and measured in parts per million). The lab will also check the oils reserve alkalinity expressed as TBN, total base number and the remaining levels of additives that are components added to the oil to make it perform properly.
If the oil is within specifications and the wear metals are below established industry levels the oil is suitable for continued use regardless of its color 
Many times I have sent a sample of used oil that was black to the lab for analysis and the lab said the oil was in good condition, suitable for continued use. So never mind the oil's color, if it's turning dark-good, it's just doing its job! 
Amsoil introduced the first American petroleum institute rated synthetic motor oil in 1972 and today is considered the world leader in synthetic motor oils and lubrication. 
By Larry Crider, Lubrication Specialist 
Questions about used oil analysis can be directed to Larry by calling 1-866-580-1008 or email

 Corpus Christi, TX 78411