[Road Ripper]

I've always used it on all my vehicles without a problem, be it used or brand new spark plugs. I use the silver aluminum kind.

At work assembling new snowmobile and ATV engines, we use NGK spark plugs into aluminum heads and don't use any antiseize. I don't know how it works out for the customers in the long run, but maybe the plugs get changed out more often so it doesn't matter.