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State of New Jersey-Department of Environmental Protection-Bureau of Mobile Sources
State of New Jersey Department of Environmental Protection
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DEP regulations stipulate that a motor vehicle shall not emit visible smoke, whether from crankcase emissions or from tailpipe exhaust, for a period in excess of three consecutive seconds. Smoke, in this context, means unburned particles resulting from incomplete combustion. Smoke does not refer to visible water vapor often emitted when starting a vehicle on a cold day. Engines emitting black smoke likely have an overly rich fuel mixture or a malfunction resulting in incomplete combustion of the fuel. Engines emitting white or gray smoke may be burning antifreeze leaking into the combustion chambers from a cracked cylinder head or block. Engines emitting bluish smoke are likely burning oil, which could be the result of various engine problems.