OK, I'm a little upset that somebody isn't flying Mom to California for Christmas but I'll try to help anyway. The object here shouldn't be to measure the spark or turn on any pretty lights. Why not drive a Sonalert to keep Mom from hearing your naughty words??? We don't need no stinkin' sparks. And why think about various spark gaps when the goal is to prevent the buildup in the first place. First, get the ol' laundry sprayer out and go crazy spraying down the matts and all the fabric that your keester isn't on. Next, rig up a gator clip, wire, resistor assembly that you can leave clipped to your belt buckle while you're driving. Attach the other end to body metal. This will help abate PKSSS (Polyester Keester Slide Static Shock). The static straps that Alan mentioned will help dissipate any buildup between earth and the body/frame but won't help with potential between you and the frame. You can keep a well watered potted plant in the back seat and one of those Peltier Effect mugs full of water plugged into the lighter socket. Lastly, take two of those big dogs with the heads that bob up and down, fill them with water, and stick them on the rear deck.
Are you ready to buy Mom that plane ticket yet?
Joe
