My guess is many xfire owners have never physically witnessed the internals of an auto engine. There are numerous places where oil can remain after the crankcase has been drained. When doing an oil change I always position the car on a level and remove the oil drain plug. I also change the engine oil filter. Before draining, the oil temperature should be at minimum room temperate. For maximum removal let the oil drain until dripping stops. After draining, I install 8 quarts, start the engine, let it run for a minute, and shut it off. After a couple of minutes I recheck the dip stick reading and add the balance needed to attain the correct level. Using this method in my opinion prevents over filling. Excessive overfilling (> 1 quart) can cause the internal crankcase and cylinder pressure to become excessively high and potentially detrimental.