Is there a plug especially designed for use with LPG (Liquid Propane Gas)?
Yes, NGK have recently (mid 2007) released 2 plugs which are designed to work more efficiently and last longer for LPG applications. The plugs feature a platinum chip in the ground electrode and a fine wire Iridium centre electrode. The thread and other metal parts are plated differently to reduce the possibility of a negative reaction to LPG. Part numbers are BKR6EIX-LPG and BPR6EIX-LPG, these will cover a large percentage of the UK car market.