For plowing it's not necessary, unless it starts getting kinked up. But usually that happens from letting to much out and It loosens up on the spool.then the cable overlaps incorrectly and gets bound up.
Just use what you have and if it gives you problems then go synthetic.
Keep the cable sprayed with a as-40 oil of some kind. I myself put grease on a rag.then I spool the entire cable out and use the greased rag to guide it back on.I do this on a slight uphill grade and use the machine to keep the cable tight and wound nicely.That way I see my winch still works properly and I know my cable it lubed and does not have bad spots in it.