I’m not certain, but I think that lubricating oils are just about the last thing that is cracked in the towers. I’ll wait to see what others have to say on this. I could be wrong. With the Babington Burner, no filtering or other preparation is required to burn crankcase oil directly except a slight pre-heating if coolish.
The objection that many have raised over the years is that the dirty waste oil has “impurities” in it that are harmful and that it would be “illegal” to burn it, etc. Harmful to your health, etc. And therefore people should not burn it for heating purposes and so on, until you are blue in the face. I dismiss these arguments because an automobile engine that has any kind of lubrication leakage past the valves or piston rings will spew this oil out into the atmosphere anyhow and we all will breath it. So the point is rather moot to me.
Most recycled crankcase oil is filtered and catalytically cracked in such a manner. Unfortunately, in many areas such service is not available. Best solution we’ve seen here is air injected combustion of waste oils – hydraulic, crankcase and transmission – in boilers and commercial heating. The prob with most private attempts to combust this feedstock is the crudeness of the combustion chamber and the high percentage of uncombusted material going out the flue and choking the neighbors out of their own homes. www.cleanburn.com is an introduction to air injection for this type of fuel. No doubt there are other resources and a person could probably develop something similar on their own work bench.