There’s an oil passage in the body of the compressor that allows the oil circulating with the refrigerant to pass into the main body of the compressor and lubricate its moving parts. Whether you are oiling or greasing, you are going to want to plug this hole. It’s pretty obvious which one it is; it has a bit of a slot to it and is the only one that goes from the head into the case. We drilled and tapped the passage to 5⁄16-inch and used a small grub screw with some Loctite to plug it. Be sure the plug is recessed below the gasket surface for the reed valve assembly when tightened.