<<SNIP>> The OEM wires have a special seal around them to prevent this, which all the aftermarket wires I have seen DON'T HAVE. <<SNIP> Although this is probably true of most plugleads, I have found a better substitue. I bought Bosch plugleads which have an even better seal around the sparks. Instead of just one rubber "top" on top of the plug it has a deep groove in the rubber so that you must put the leads on more carefully so the top slides completely around to cover the plugs well. These have been more effective in my opinion but that may just be me.