Speedometer Cable Lubrication

Aight-got the cable hooked up and everything, and I have been meaning to lube the cable for some time. It's jumpy at low speeds, and will fluctuate +/- 3mph above 25mph. Is there a quickie way I can lube the cable? I've heard graphite, bicycle chain lube, and plain ol grease, all of which I have. What gives the best results?

I've used a product called Tri-Flow that's got teflon in it. You can get it at most hardware stores and at bicycle shops. I then took a piece of heat shrink tubing (that will fit over the cable end at the speedometer) and shrink it onto the sprayer-straw. Then I spray it for about 10 seconds over the speedometer end. This usually last a couple of months before the jumpiness comes back. Good Luck!