MolaKule I appreciate the link you provided. Some things I still don't understand, though.
Other than being an inky black substance, etc, what exactly is it? Why is the oil not able to hold it in suspension? I thought that was a big part of what oils were supposed to have additives for.
Why does low crankcase temp contribute to it? Is it primarily because at low temps the chemical action of the oil to break it down and dissolve or suspend it is not sufficiently strong? What oil characteristics help with that?
Why does it occur when there are high combustion temps?
Why does it occur when you have lean burning?
Still trying to understand it more fundamentally.
Thanks again for the earlier reply.