Dyes, of course are ineffective
in dark oils but in light colored products give a distinctive appearance. In
ATF it has been suggested that if the lubricant were colored, any leakage from the transmission could be
distinguished from that
coming from the engine. In such case the mechanic would known which unit
to repair. Actually, colored ATF has been qualified.
If dyes are added to gear oils
they should be oil soluble and also stable under the conditions of operation,
such as heat and the presence of other additives. Oil soluble red dye has been
used in ATF. Fluorescent dyes may also find application in transmission fluids.
