How long can stock spark plugs last? I'm thinking of upgrading mine, I'm at almost 10,000 miles, I was wondering how long before I have to replace them (still short on money). When I do replace them, i think I'm going with Denso Irridium plugs (about 48 bucks from sparkplugs.com, which isn't too bad). How long does the Denso last? Longer than stock I'd hope

 

Nobody's put enough miles on their car to give dead on examples, but they're said to have good long lives from what I've read at least.

 

I had my plugs till 25,000. I replaced them with NGK Iridiums and man were the stock plugs dirty. That's my 2 cents

 

i would replace them at about 12k miles with some factory ones, you'll notice the difference. i replaced mine at about 23k with factory one, there was a huge difference.
https://www.evolutionm.net/features/...rtech&id=15&s=

hope that helps

Link

 

Random question to those that have changed their plugs. I think it's pretty well known that the few members who have changed their own plugs have said the originals look black and cruddy when they take them out.

However, out of these people, have any of you noticed either the center electrode or bridge part of the plug heavily eroded where the spark would be fired across the gap? Like excessively pitted, shallow depth, etc?

I've got a a small idea as to why our plugs look like junk when people are taking them out, but would like some feedback which will help me to prove or disprove it.

 

i changed mine after 2,000 miles it might have been less but they weren't dirty at all really

 

Plugs normally get brown/black with use, heavily eroded or electrodes that have fallen off are due to heat stress, detonation, using cheap gas, or somewhere along the fuel system something is terribly wrong.

Get your car checked out ASAP if your plugs come out missing electrodes.

 

I know all these things about plugs and wear - thanks but I wasn't asking for that. I was specifically asking those who changed their own plugs what their electrodes looked like.

Where I was going with this.... If there is excessive electrode wear or pitting noted, I think it's useful to remember that the DIS setup fires each plug on each revolution of the crankshaft. So we're creating a high voltage spark on both the compression and exhaust stroke. If we had 4 packs instead of two, each plug would fire once every other revolution of the crank - only on the compression stroke. Of course it's cheaper to install only 2 packs vs 4, so the bean counters won this one at Mitsubishi.

The ignition setup means that the duty cycle of the plug is 2x as much in relation to some other inline four(s) I've changed plugs on. A plug fired twice as often over a given number of miles would most likely have more wear around the electrode(s). I was trying to find out how well the stock plugs held up after a typical changeout interval such as 10,000 or 15,000 miles.

 

changin mine this week, i will be hitting 12000 miles i will take some pic's and post them, hopefully they will answer your question
slightly related note: i will be replacing them with denso iridium plugs hope to see some sort of a difference

 

for denso! hope to get sum soon as i get 48 bucks!!!

 

I changed mine early on. They weren't awful, but whatever...I still have them and they're still in the same condition (put em in the Denso box). If I remember tomorrow I'll grab em and take some pics for you. Hope that helps.

 

here are pics of my plugs after 12k i replaced them with denso iridium not noticing a difference at all but i have been told that they only help if you have some sort of forced induction or nitrous well anyway they could have stood some more miles probably made it to 20k at least

 

well forget this as it turns out the pic doesn't look as good on here as it does for me here i will figure this one out later

i will describe what you can't see around the arc there is some slight carbon build up and basically the whole thing is a little dirty and the u groove is worn

 

so how long do irridum plugs last?

 

They have a 250,000 10 year warranty, but I find it hard to believe they last that long.