detergent oil - lubricating oils with special additives, used in some internal combustion engines to hold sludge particles in suspension and to promote engine cleanliness
The outer surface of the reflex reflector and, in particular, the illuminating surface, shall be lightly wiped with a cotton cloth soaked in a detergent lubricating oil. After about five minutes, the surface shall be cleaned. The CIL shall then be measured.
