Time for me to replace my spark plugs on my 06 Opti DFI. MY manual calls out the plug part number, but also calls out an optional plug. Anyone know the difference? Is one better than the other? Not sure if there is a service bulletin for another part number plug?? Thanks! Spark Plug – NGK IZFR5G gap 0.8 mm (0.031 in.)Optional Spark Plug – NGK PZFR5F-11 gap1.1 mm (0.043 in.)Last edited by brewcat on February 26th, 2011, 2:43 pm, edited 1 time in total.