I bought a new set of A/C iridiums when I bought new tires, at 96k miles. I stretched the life of my Affinities to that point, and chickened out of going farther with them. But, after getting the new tires, and changing the filters and oil on my Panel, my gas mileage went back up to 30mpg from 28.7mpg overall (I have never reset the DIC). So, I thought I'd stretch the life of the plugs as far as I could, just as a test (I test everything). So, now at 108950 miles, the mileage has started dropping again...to a new low of 27.4mpg, and the idle is started getting a little erratic (smooths out fine under accel, or when the A/C is on). If anything, the little 2.2l seems stronger than ever, but I know its time to change the plugs. How long did some of you guys go until you did it? It's still amazing to me: the life of the plugs and engines these days. I used to have to change plugs, points, rotors, etc. every 6k to 10k back in the "good old days".

 

GM says 100,000 miles. And I believe them, I changed mine around 80,000 old ones were immaculate.

Iridium sure is better than iron.

 

I changed the plugs in my '04 2500HD Chevy 6.0L at 99500 miles. They looked fine. But, the truck actually ran worse for a coupla days with the new plugs and wires. Go figure!

 

Yup, 70-80,000 miles seems to work out just fine here as well.


Oh yeah - those points, plugs, condenser, rotor and cap changes were the norm (I always carried a spare set of points and condenser in the toolbox in the trunk, and the last cap and rotor I swapped out if they were still serviceable)- and setting the points gap and dwell was a pain - LOL - ahhh what's dwell they now ask.

 

LoL whopper is living in the past weak up! Well the stock plugs are the best changed mine at 90,000 and do your self a favor when you change them put like a dab of anti -seize compound on the thread toward the top and also do this when engine is cold do to the aluminum block ... Air filter at 50,000 if you do this you will get good mileage and record everything you did using your smart phone

 

We owned ours for 6+ years/60000+ miles and I never changed the plugs. The other two that I occaisionally work on are both still under 100k and have the original plugs, as far as I know.

 

I agree with the anti-seize and aluminum heads...I've been careful with the CNC'd Brodix heads on my Chevelle (especially since I have to index the plugs and remove body/suspension parts to even reach a couple...and the old VW Beetles I had owned, all had to have threadserts installed on one or more plug holes due to thread strip-out. I change my air filters at 30k or less; this one is only 8+k miles old, and the gas mileage is dropping anyway...plug change time!

 

Lack of harmful deposits has nothing per se to do with iridium.

Ordinary copper core plugs should give the best performance - at the price of longevity. The softest electrode metals are usually best, but the shortest lived.

 

I was using "immaculate" in the conception sense I.E.: Virgin, Unused; not the "kitchen" sense I.E.: Clean, No dirt.

My plugs after 80,000 miles appeared as if they were unused, and the gap was as if unused. The only sign of use was outside of the engine insulator showed some normal heat "browning".

 

I'm going to do ours soon. Some 86 k miles on them. Hope they look as nice as yours.

Was it uneventful breaking them loose?

Let's say that even with a stone cold engine it just feels like too much torque to break the threads loose. Well, you could use some penetrating oil, but then what if it even slightly contaminates the new plugs - if not a drip, then a bunch of oily smoke on start-up? In reality, I'd end up using brake or MAF spray to clean off oil from threads on head, and have a bunch of that stuff ready to light off too. I want male and female threads dry and clean, then apply a small bit of anti-seize. I guess you could put the old ones back, drive around, then next day do the job again with new plugs.

Keeping anti-seize away from any possible contact with business end of plug is a similar problem.

When you plan on leaving these expensive plugs in for 100 k miles, the quality control issues go way up.