[ainarssems]

I think what they do is heat up the transmission to working temp so that thermostat opens, drain the sump, fill with fresh oil. Then hook up the "sucky pumpy squirty thingamajig" in the transmission radiator loop to collect dirty old oil from there and start the engine, Machine then measures amount of oil collected and pumps the same amount of fresh oil in at the same time. You can see extracted oil either through clear tubing or a window and when you see fresh oil coming out you know all oil has been changed. I suppose they might be heating up new oil as well to keep thermostat open during procedure.