When trying to figure out if a liquid is conductive or not, you want to set your multimeter to continuity, not measure voltage, unless you keep the black probe on chassis and dip the red one in to see if you get 240v. When you submerge your probes in the liquid meter shouldn’t beep while set to readout continuity. But in order to be sure you need to get a sample of one or two drops, place it on a piece of plastic or glass and test with that while your probes are almost touching.
@@1lluv I know it's oil, but it still depends on the water temperature to cool the oil temperature, and then the hot water circulates through the booster pump pipes to the heating radiators in each room.