Something too consider. I had recently bought my car and had no idea what oil or milage was on that oil so I did the AutoRX with a change. Dumped the AutoRX in the engine filled the AutoRX bottle with oil and then dumped the rest in the crankcase it was a 5 quart bottle so filling the AutoRX bottle with oil stopped me from overfilling. A little over 1300 miles into the cleansing the motor got a little noisier, I changed the filter and topped off with the oil in the AutoRX bottle, didn't get it quite full but close and well into the safe range(will depend on how much comes out in the filter change). Running nice and quiet again and I will probably drain it at about 1700 as long as it stays quiet.