I have been doing some research into Platinum and Iridium spark plugs for my VX, unfortunately I am coming to realize there are none made
However in my search I have found that the Denso website (
DENSO SPARK PLUGS)
Has the plug gap for the D15B8 (CX) and D15Z1 (VX) @ 0.032" instead of the regular 0.044" for pretty much every other Honda Civic D series engine, except for the GX which is a natural gas D Series engine that runs a compression ratio of 12.5:1 !
NGK has the gap @ 0.044" for the CX & VX.
I also checked plug gap on a 1988 Toyota Celica All Trac Turbo is 0.032 on both NGK and Denso (O.E. for Toyota)
A regular 1988 celica is a 0.044" gap
To sum it up I believe that Denso has spec'd a tighter gap on the VX, CX, and GX is because of high EGT in running Lean Burn mode and Natural Gas in the GX's case.
I only have 10k KM on a set of NGK's in my VX which I gapped @ 0.044 but I may check my gap and regap if necessary on the low side of 0.044"
Cheers!