Three machines: 2002 YZ250, 2001 Gas Gas XC250 and Homelite weedeater--all using Mobil 93 and Mobil MX2T, the YZ and the wacker get tan plug readings while the Gasser is gray. All dry and look good (no deposits). Any ideas what influences the different colors?
Do a search on plug readings, there have been some very good threads not long ago that will tell you everything you wanted to know about what influences the color of a spark plug.