Measuring gap/gapping iridium spark plugs

[DrDonnyBrago]

Morning all,

When measuring the gap on an iridium plug is it best to use a wire type spark plug gauge, a disc type spark plug gauge or a feeler gauge?

I was under the impression the feeler gauge is not suitable and one of the others can damage the tiny iridium centre electrode.


Anyone know which is the correct tool to use to measure the gap on an iridium plug?

If anyone needs to know the plug type (not sure why) they are NGK IMR9a-9h plugs.


Cheers .

[Bezzer]

The official manufacturers line is you don't measure or gap iridium plugs, use straight from the box and don't bother again until they are replaced. Apparently doesn't take much to scratch the coating so you pays your money and takes yer chance, I'd use a wire type gauge , though saying that I don't bother with Iridium plugs myself, I'd rather replace standard ones regularly than pay 2-3 times the price for Iridium.
____________________
I used to be indecisive but now I'm not quite so sure.

[Robby]

I have never seen an iridium plug wear enough to need gapping, but not need replacing. To my knowledge, the iridium coating is very hard and very thin. Once it has worn away, which takes a long time, you replace the plug. If the gap has opened up at all, the iridium coating has worn away.

I can't remember the last time I saw a spark plug worn enough to need gapping, apart from on some of my dad's garden machinery. Garden machinery spark plugs don't seem to be as tough as those used on everything else, nor are they working in such carefully controlled circumstances. I serviced the woman's car at the weekend. Changed the plugs as a matter of course, but the previous set of (standard copper NGK) plugs had done 30,000 miles and were maybe 10% worn. They would seize into the head long before wearing out.

It's a shame that plug changes are still such an ingrained service item. There are more threads in the forum about people overtightening a plug and breaking their cylinder head than about worn out spark plugs.

[DrDonnyBrago]

Appreciate the comments guys, it was more about checking the gap on the new plugs before installing them, there is a gap specified in the workshop manual and I wanted to check the new ones were set to that before using them.

Was reading this on the NGK site:

https://www.ngksparkplugs.com/techinfo/spark_plugs/installation.asp

[paddlesat16]

[The Shaggy D.A.]

As an aside, anyone actually noticed any difference with Iridium plugs? I put some in a few months ago, it's made squat difference to MPG :-