Engine Oil - Dye and Discoloration
86chevy16NUMBER: 86-B-29
GROUP: 6-Gasoline Engine
DATE: January, 1986
SUBJECT: ENGINE OIL DISCOLORATION
MODELS: ALL 1985-86 MODELS
General Motors Corporation engine plants utilize engine oil dye from time to time in various engines as an aid to oil leak detection during the manufacturing process. The dye causes the oil to glow bright yellow when exposed to a "black" light. There are several sources for "black" lights, such as Kent Moore Tool, Snap-On Tool, Mac Tool, etc. Some of the dye material used gives the oil a slight red or green tint, and in some cases has been mistaken by service personnel for automatic transmission fluid or engine coolant. If the engine oil was contaminated with engine coolant, the oil would be a gray or "milky white" color. Trans- mission oil would tint the engine oil light pink, however, it would not glow bright yellow when exposed to a "black" light. Dealers should be advised that the dye is in no way detrimental and that the oil should not be changed if this condition exists. If the engine oil is suspected of being contaminated with foreign material, a small sample (1/4 Cup) should be exposed to a "black" light. If the oil sample does not glow bright yellow, it is possible that the oil is contaminated and should be changed to prevent engine damage.