I've got a Griots oil extractor and it works great. Takes at most 15 minets to extract ALL the oil. I've actuall removed the oil drain plug after extracting the oil to see if I got it all. Hardly a drop came out. You must be running very heavy oil. Next time you change, drive your car around the block to warm the oil then it should come out much faster. Make sure you have tight connections on the extraction tubes, no vacuum leaks. Use the extraction time to change the oil filter.