NGK do not recommend gap adjustment for precious metal spark plugs.
A variety of techniques are used to adjust electrode gaps. An appropriate method and tool should be used for gap adjustment although it has come to our attention that a variety of improper methods are used that lead to implications.
When adjusting the electrode gap, the gap may commonly be made too small, as such, the gap may need to be opened slightly. Typically some customers use a lever such as a flat screwdriver to pry open the gap. Traditional Nickel plugs have a solid piece Ø2.5mm centre electrode that may withstand such force. Precious metal spark plugs however have Ø0.6mm fine tips that are laser welded to the centre electrode. These tips are very fragile and not designed to withstand any force. As such NGK will not provide warranty for the breakage of precious metal centre electrode tips.
It is possible to adjust the electrode gap on precious metal spark plugs using an appropriate method that will not place any force on the centre electrode tip.
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Thank you to NGK for the great recommendations and tips.