Back to cars.
Solved why the 99Civic died-fail ignitor module,. Which probably was the problem of poor power, poor mileage, bad oxygen sensor computer read.
So since I hadn’t changed spark plugs in untold years, I got some cheap, standard spark plugs. I pulled the plugs and discovered that I had platinum that were only slight out of gap tolerance. All the plugs were out recommend gap by the same amount (not much), and had the same color.

So I thought since the platinums looked so good why would I replace them with new cheapie plugs. So I regapped the platinums and reinstalled.

Did I do right or should I scrap the platnums and replace with the cheapies or spend a few dollars more for better sparks?

@longprime not to be disrespectful, but platinum plugs are not supposed to be regapped.

Since they “might” be compromised at this point, I would install the new standard plugs. They’ve already been paid for, after all.

As long as the plugs are the correct ones for your application. Hard for me to say, because I don’t know what you got and I don’t have your owner’s manual.

Yep I agree, they are too brittle to be re-gapped. You don’t want the electrode to break off inside the engine.

the electrode is flush to the ceramic insulator. Is the danger really cracking the insulator? Well I got 400 miles since the regap. Should I still swap out and if I do and find that the platinums are OK, can I still use them?

Platinum is more expensive than gold. And I would hate to subsitute it for copper.

Personally, I’ve gapped a lot of platinum plugs with no problem. The main thing is to avoid putting pressure on the center electrode.

Sometimes one particular spark plug is used for different makes of cars and engines that require different plug gaps. It’s not logical to think that a plug used in 2 dozen different applications is going to come out of the box pre-gapped.
With a wider gap I gently tap the side electrode down. With a narrower gap I use needle nose to widen the gap and then either narrow it back down by tapping or using a plug gapping tool. (The latter kind of resembles a pair of pliers and no matter the method, very carefully.)

For what it’s worth, a new platinum plug will not put out a better spark than a new standard copper core plug. The main difference is that the platinum plug usually has a longer lifespan and is usually easier on the coil.

The car makers also want to make sure they’re not having to pony up a ton of warranty plug replacement costs under the Federal emissions performance warranty…

Me, I would put in new plugs of the same type Denso or NGK as it had coming out of the factory.
Copper core or platinum, whatever.

With 400k I concur w/@circuitsmith the better course is new plugs. Micro-cracks in the insulator could exist, as could micro-carbon tracks. It might be ok, but I don’t think it is worth the gamble.

I always put the exact plug the owner’s manual recommends, which for my Corolla is just a run of the mill NGK plug that costs less than $3 each. Replugging is such a simple chore on a Corolla, it takes about 15 minutes once you have all the parts and tools assembled. Sometimes I have to order that particular plug up from the parts stocking warehouse, but using that plug has never resulted in any ignition system problem in 200k Corolla miles. I usually re-plug every two years, which is about 20K miles for me. Sometimes 30K. By the time I replug, the gap has grown wider, enough that is has on occassion – if I go to 30K – caused some pinging on steep hills. The new properly gapped plugs always end any pinging.

Actually a platinum plug does make a hotter spark. Not because of the material but because it has a smaller tip. The smaller tip concentrates the corona and make for a hotter spark. You could do the same thing with a copper tip or iron tip, but because they are softer, they wouldn’t last very long.

But whether you really need the hotter spark or not is a different story. Once you ignite the fuel air mixture, it will burn at the same rate whether the spark that ignited it was 50% hotter than needed or 150% hotter. If the spark is sufficient, then a hotter spark will not improve your engines performance. It will not make it more powerful, get better gas mileage or be more efficient.

The real advantage to platinum or iridium tipped plugs is longevity. For the manufacturers, the less maintenance required by the original buyer, the happier the original buyer.