I’m running NGK Laser Iridiums in my TA and they’ve about 32,000 miles up now over the last 4 years or so, engine is running fine, my driving is generally mixed urban, how long should I expect these to last before replacing?

Our Mazda uses Iridium, their service interval is 5 years or 60,000 miles which ever is sooner, so I'd say 5 years?
That's what I'm assuming in our Fiat too.

They're like any other plug. The electrode gets burnt away with use, so the gap increases. If I remember right, the advice for Iridium plugs is "do not adjust/re-gap"... though I'm not sure why not, so that makes me wonder if I'm correct.

Any road up... when the gap gets too big (not sure what the gap should be) tweak the plug gaps for a bit more use out of them and start saving up for some new ones.

My Iridium plugs (Alfa T/Spark.. maybe used more revs) lasted 60k just about.. but looked very ropey by then. Again, it was still running fine. Plugs can be changed anytime though.. there's no need to wait for a service interval.

Ralf S.

Friend with iridium plugs on a Renault has never changed them. Wanted for nothing else and done 130k. My Panda done 42k on originals. The bi annual change on schedule is advisory. But after read main dealers can charge £100 I wasn't entertaining that.

Modern systems can cope with quite large gaps I think don't gap them is because they are ready gapped and the central electrode is very easy to break given it's tiny size?
I paid £30 or our Denso Iridium plugs.

Ralf S. said:

If I remember right, the advice for Iridium plugs is "do not adjust/re-gap"... though I'm not sure why not, so that makes me wonder if I'm correct.

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You do remember right, and for good reason. The iridium tip is both extremely hard and extremely brittle; if you apply any pressure to it, there is a real risk of it breaking off inside the cylinder, which obviously is a seriously bad thing.

Never check the gap using a ball type gapping tool; some say even checking it with feeler gauges is a risk.

I generally change plugs 'on condition'; IIRC this used to be official Ford servicing policy back in the day. I've got iridium plugs in the Panda which are still perfoming just fine after 80k+; I've also chucked away conventional copper core plugs in the 500 after less than 6k.

The only thing I'd caution if keeping plugs for high mileages is to be wary of thread corrosion; anti seize is your friend.

I just had a misfire in the Mares (1.8 so coil per). The NGK iridium's were done for after 70k and it looks like they have taken a coil with them. They were embarrassing, the Earth electrode more than 1/2 eroded and a gap of about 3mm so the centre burnt back as well I have them in all my cars but it's the everyday workhorse that does the mileage. I still like them, but it's change at 50k from now on