This is gonna sound like I'm trying to be a "know it all" which I'm not, but the only SM motors I know of that use grease as lube are Singers. If you pull a motor like that one apart you'll usually find a felt washer surrounding a bronze bushing. The felt holds the oil in the bushing area as the bushing absorbs it.
If your motor gets hot enough the grease might melt into the bushings ... "if" it's not Tri-Flow. If it is get as much out as you can and oil it with sewing machine oil. I'd oil it anyway.