It is to keep the gears lubricated. The pot just had a couple screws holding it on. I pulled them off and cleaned the grease out with a screw driver end - then I painted it with the kerosene and turned it a bit to wash it out good inside where I can't see. Lots of goo came out of there. I painted until it ran clean again. I'll pack it full of grease when I get that far. You all have to stay tuned in a week or two for part 2 of the continuing saga of 'Mr Ed the 319w before his time sewing machine'. I am fascinated by the engineering on the older zig zag machines. Each one is unique isn't it? I'm pretty sure I need to do something to the stitch length regulator - it doesn't travel.