This is probably obvious but if you haven't checked your spark plugs in a while it's probably worth it to pull them and take a look. I changed mine this afternoon right around the 105,000 factory reccomended interval and checked the gaps on them. They were at .070! Not sure if the tech that did the spark plug TSB overgapped them or if it's just from being worn down.

The car ran well overall with some occasional stuttering between 2-3K rpm at more than half throttle (no CEL). Other than that I was only getting 22 mpg with reasonable mixed driving (60% highway, 40% local roads). After the swap the engine response was dramatically better and felt like I picked up an easy 15-20 rwhp. So just a friendly reminder, check your plugs!

 

Thanks for the info, I'll check tonight.

 

From my experience, that's what happens to the Laser Platinum plugs while in use. When I changed them on my 2003 G35 at 60K miles, the electrodes were just little bitty nubs already. I think the platinum plugs should be changed at 50K miles. I don't know why the manufacturers say they are 100K+ plugs.

In any case, don't try to re-gap them when you check them. Just replace them if you think the gap is getting too large for your comfort.

 

+1 I agree. I also went with NGK BKR7E's this time instead of OEM plugs in anticipation of going S/C soon. They were easily to find (local O'Reillys) and only $2 a piece. The manufacturer gap was at .035 but I bumped them up to .040 and will gap the next set down when I put the blower in.

 

In my European manual they say to change them every 100.000 km (or 5 years).
100,000 km = 62,150 miles.

I think that if the little platinum plate on the base electrode is gone, the plug is gone, as long as its there it's good.
On an old set of NGK's I just measured, the gap still is 1.1mm after ~50,000 km.

The OEM NGK plugs come pre-gapped @ 1.1mm +0/-0.1 IIRC.

 

I had 74000 mile on original plugs. Idle a little rough, off the line under powered seems to lag. Mileage has been 20 city/ 24 hwy at best. Checked the gap 47 thous and center electrode was really worn down. I have been getting 23city/28 hwy

bought some New NGK #7746
$61 shipped to my door sparkplugs.com, took about 20 minute to take my time
around town everyone wanted 95-105 phuk that

Had the valves adjusted last week, last adjust was at 35000 miles

Car runs great !!

I was going to replace with #7772 OE but I spoke with NGK directly they said go with IFR7G-11KS, 7746 Laser Iridium

 

What's the recommended mileage to change Spark Plugs?

 

I just recently changed mine at 56,000 miles with OEM. The gap had grown to 0.050 in one plug and nearly 0.055 in the other plugs. My mileage had slipped to 21-22 mpg in mixed and is now back up to 24 mpg.
I would recommend changing them out no later than 40,000-45,000 miles based on them being that far out of spec at 56K miles.

 

The OEM (red box for NGK) come pre-gapped, and should not be regapped if out of spec. Just replace them with OEM (for a stock engine).
I tried the one step cooler ND Iridium plugs for about 10,000 miles and noticed no advantage at all. I pulled them after a few folks had engine failures associated with the ceramic insulators separating and falling into the combustion chamber (these were all FI cars).
I don't think I'll go over 35,000 miles next time based on my experience with the first set.