Originally Posted by
BEagle
In the rear part of the fueslage there was a chart on the side of the compartment which gave guidance as to the colour of engine smoke observed and the likely engine fault. Blue, white, black....it was fascinating!
My dad told me about that years ago, although relating to car engines.
Blue - oil, White - coolant, Black - fuel.
Not sure where that leaves white on an air-cooled radial...