I wondered on this myself, as I have just bought the same kit second hand, so no instructions. It usually takes I think 3.5l to fill the engine..not sure how much extra is needed when the cooler kit is fitted. I take it all the oil goes back to the sump when turned off, so you can't fill, run, turn off, check level, fill and turn back on like when you fit an oil filter? Seen some coolers located real low down thou..