I keep it simple... heat it to around 95C or so, hold it there until it stabilises, bump it up slowly to 100, once water is boiled off I push it up to 110 and hold it there for a while... stirring continuously ..... shut down the stirrer and let it cool... when it gets below 100 I start filtering it thru a 5 mic filter by gravity, leaving the last 25% to 30% in the tank.... I don't filter from the bottom, but about a 1/4 way up... once fully cooled any settled crap is drained off the bottom and the tank is filled for the next run.. I pump heat in via 2 elements, one of 4 or so kw, the other is 1.5 kw... both on for fast, big one only for slow, and small for holding and very slow heat up.. they are normal hot water elements, but the smaller is for hard water, so it has a lower heat density... total vol oil processed is about 70 L a batch or thereabouts..
Once all cooled and filtered, I adjust visco to about 25/35 and throw it in the tank.... usually use dino to adjust, RUG gives a bit of a knock ....
While heating, I am sure that the small percentage of RUG etc in the gunk is boiled off... these are quite minimal, hardly any odour too, and by the looks of it are not worth condensing for use as a dilutant later...
That's about it...
If you spot any things in my method that I have missed, let me know!
Regds
Ed